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S|j&'. i M -apqflfltyjftffi ’ ' ' “: "■ RADIOLOGICAL 
DEFENSE 
Vol. IV 
A 
Manual 
Prepared by the 
Armed Forces Special Weapons Project Radiological Detense, Vol. IV 
RADIAC 
An Introduction to Radiological 
Instruments for Military Use 
by 
D. C. Campbell, LCDR, USN 
This document contains information affecting national defense 
within thfc meaning of the Espionage Laws, Title 18, USC, Section 
793, 794. The transmission or revelation of its contents in 
any manner to an unauthorized person is prohibited by law Page 
Index to Illustrations v 
Foreword vi 
Chapter 1. Introduction , 1 
Chapter 2. Radiation in General: 
2.01 Introduction 3 
2.02 Electrically Neutral Radiation 4 
2.03 Electrically Charged Radiation 4 
Chapter 3. Ionization Chamber: 
3.01 Introduction 7 
3.02 Pocket Dosimeter 7 
3.03 Drift Meter 8 
3.04 Pocket Chamber 9 
3.05 Electrometers 9 
3.06 Chamber Characteristics 10 
3.07 Chamber Window 11 
3.08 Wall Material 12 
3.09 Pressure and Type of Chamber Gas 12 
3.10 Chamber Volume 2 13 
3.11 Electronic Characteristics 13 
3.12 Ionization Chamber Instruments 14 
Chapter 4. Gas Amplification 15 
Chapter 5. Proportional Counter: 
5.01 The Proportional Region 19 
5.02 Proportional Counter Probe 19 
Chapter 6. Geiger Mueller Counter: 
6.01 Avalanche Ionization 21 
6.02 Quenching the Discharge 22 
6.03 Portable Geiger Mueller Detector 25 
Chapter 7. Scaling Circuits 27 
Chapter 8. Count Rate Meter 29 
Chapter 9. Crystal and Chemical Detection: 
9.01 Excitation 31 
9.02 Chemical Dosimeters 31 
9.03 Scintillation Counters 32 
9.04 Other Possibilities 33 
Chapter 10. Photographic Dosimetry; 
10.01 The Film Badge 35 
10.02 The Densitometer 35 
10.03 Film Processing 36 
Chapter 11. Cloud Chambers and Accelerators 39 
Chapter 12. Shape and Characteristics: 
12.01 Introduction 41 
12.02 Physical Characteristics 41 
12.03 Electrical Characteristics 43 
12.04 Radiological .Characteristics 43 
TABLE OF CONTENTS Page 
Chapter 13. Calibration 45 
Chapter 14. Operational Instrumentation: 
14.01 Available Instruments 47 
14.02 The Alpha Particle 48 
14.03 The Beta Particle 50 
14.04 The Gamma Ray 51 
14.05 The Field Laboratory 55 
14.06 Other Establishments 57 
Chapter 15. Description of Actual Instruments: 
15.01 The Field in General 59 
15.02 Pocket Dosimeters and Pocket Chambers 59 
15.03 Quartz Fibre Survey Meter 63 
15.04 Ionization Chamber Survey Meter 64 
15.05 Portable Alpha Proportional Counter 69 
15.06 Geiger Mueller Counters 70 
15.07 Photomultiplier Survey Meter 79 
15.08 Film Badge > 81 
References 83 
Appendix I. A-N Nomenclature List 85 
Appendix II. Glossary of Terms Concerned With Radiac Instruments 87 
Index 89 INDEX TO ILLUSTRATIONS 
Page 
Figure 1. Work is under way to develop satisfac- 
tory instruments vin 
Figure 2. Gamma ray absorption 4 
Figure 3. Laboratory type electroscope 7 
Figure 4. Pocket dosimeter 8 
Figure 5. Reading the pocket dosimeter 8 
Figure 6. Charging a pocket dosimeter 8 
Figure 7. Schematic drawing of quartz fibre survey 
instrument 9 
Figure 8. Personnel pocket chamber 10 
Figure 9. Wearing a pocket chamber 10 
Figure 10. Charging and reading the pocket 
chamber 10 
Figure 11. Alpha-Beta-Gamma portable ionization 
chamber survey meter 11 
Figure 12. Ionization chambers 12 
Figure 13. Ionization chamber circuit 13 
Figure 14. Electrometer tubes 14 
Figure 15. Resistors for electrometer circuits 14 
Figure 16. An ionization chamber survey meter 
goes ashore during landing maneuvers. 14 
Figure 17. Ionization chamber survey meter 15 
Figure 18. Gas amplification 16 
Figure 19. Counting chamber and circuit 16 
Figure 20. Pulse size as a function of voltage from a 
chamber exposed to a constant energy 
source of radiation 17 
Figure 21. Portable proportional counter survey 
meter 20 
Figure 22. Parallel wire proportional probe 20 
Figure 23. Geiger-Mueller tube pulse 21 
Figure 24. Geiger-Mueller tube characteristic curve. 22 
Figure 25. Neher-Harper vacuum tube quench 
circuit 23 
Figure 26. Tubes for portable Geiger-Mueller 
counters 23 
Figure 27. Laboratory Geiger tubes 24 
Figure 28. Diagrammatic sketch of a portable Geiger- 
Mueller Survey Meter 25 
Figure 29. Geiger-Mueller counter in use 26 
Figure 30. Simplified scale of two scaling circuit 27 
Figure»31. Schematic diagram of a scintillation 
counter 33 
Figure 32. Film badge 35 
Figure 33. Film badge carried in shirt pocket 36 
Figure 34. Schematic arrangement of a densitometer 
used to determine film badge readings. 36 
Figure 35. Densitometer in use 37 
Figure 36. Characteristic curve of a film badge 
emulsion 38 
Figure 37. Medical records 38 
Figure 38. Existing equipment tried during field 
problems is found to be lacking in 
many characteristics 42 
Page 
Figure 40. Checking meat for alpha contamination 
with a poppy-type portable propor- 
tional counter 49 
Figure 41. Geiger counter in use with beta shield 
open to increase detection sensitivity 
in checking for ground contamination. 51 
Figure 42. Ionization chamber being used for 
gamma survey work by a shipboard 
damage control team 53 
Figure 43. Individual dosimetry 63 
Figure 44. Helicopter ground monitor 54 
Figure 45. Decontamination 54 
Figure 46. Checking hand contamination 55 
Figure 47. Laboratory 56 
Figure 48. Dosimeters and chargers 60 
Figure 49. Electrostatic dosimeter charger PP- 
354A/PD 61 
Figure 50. Pocket chambers and charger-reader. _ 62 
Figure 51. Victoreen minometer type charger- 
reader 62 
Figure 52. Nuclear Instrument and Chemical Com- 
pany model 2050 charger-reader 63 
Figure 53. Radiac meter IM-7A/PD quartz fibre 
drift alpha, beta, and gamma survey 
meter 63 
Figure 54. AN/PDR-T-1 gamma survey ioniza- 
tion chamber 64 
Figure 55. National Technical Laboratories ioni- 
zation chamber gamma survey meter, 
model MX-6 (IM-40/PD) 65 
Figure 56. Victoreen model 247A gamma chamber 
survey meter (IM-3/PD) 65 
Figure 57. Tracerlab Cutie Pie (IM-5/PD) 66 
Figure 58. National Technical Laboratories model 
MX-2 beta-gamma survey meter 66 
Figure 59. Rauland Zeus 67 
Figure 60. The AN/PDR-20(XN-1), an experi- 
mental model military Zeus 68 
Figure 61. Victoreen high-range proteximeter 68 
Figure 62. AN/ADR-l(XN-2) Airborne radiation 
detection system 69 
Figure 63. Original poppy type portable alpha 
proportional counter 69 
Figure 64. Nuclear Instrument and Chemical Com- 
pany pee wee proportional alpha 
counter model 2111 70 
Figure 65. AN/PDR-10 poppy type proportional 
alpha detector 70 
Figure 66. El-Tronics model SM-3 Geiger counter 
(AN/PDR-26) 72 
Figure 67. National Technical Laboratories model 
MX-5 Geiger counter (IM-39/PD).. 73 
Figure 68. Nuclear Instrument and Chemical Com- 
pany model 2610 Geiger counter 
(AN/PDR-7) 73 
Figure 39. Gamma calibration 46 Page 
Figure 75. Geophysical Instrument Company mod- 
el 600 monitor 78 
Figure 76. Kelly-Koett model K-240 hand and 
foot counter (AN/UDR-3) 79 
Figure 77. AN/UDR-10 five-channel counter for 
detecting beta-gamma contamination 
of the hands and feet 80 
Figure 78. AN/PDR-11(XN- ) alpha survey meter. 81 
F igure 79. AN/PDR-18 gamma photomultiplier 
survey meters 82 
Page 
Figure 69. Victoreen Instrument Company model 
263A Geiger counter (AN/PDR-5)._ 74 
Figure 70. Recent commercial improvements in 
portable Geiger-Mueller survey 
meters 74 
Figure 71. Geiger counters AN/PDR-8(series) 76 
Figure 72. Geiger counter AN/PDR-15 76 
Figure 73. Radiac set AN/PDR-27 77 
Figure 74. The AN/PDR-T-2 Geiger-Mueller sur- 
vey meter 78 FOREWORD 
This volume is the fourth of a series of Radiological Defense Manuals 
issued by the Armed Forces Special Weapons Project for training purposes in 
the Department of Defense. The objective of Volume IV is to present certain 
phases of the radiological instrumentation program in such form as to assist 
defense personnel in preparing themselves for the complex detection problem 
which must be faced during atomic warfare. 
Aspects of the program are presented as seen today. It is anticipated 
that research and development now under way will make many of the in- 
struments herein described obsolete within a period of 18 months. 
The volume combines with the description of specific instruments a basic 
consideration of the mechanism of radiation detection and an indication of 
possible operational use, so that field personnel may be given a comprehensive 
picture of the role to be played by radiological instrumentation during atomic 
warfare. 
x & a. 
K. D. NICHOLS 
Major General, USA 
Chief, Armed Forces Special Weapons Project 
January 1950 Figure 1. Work is under way to develop satisfactory radiac instruments. 
Shown are representative models of both commercial and military portable instruments of types which are of immediate interest to the Defense 
Establishment. 
VII i RESTRICTED 
RADIATION INSTRUMENTS FOR MILITARY USE 
Chapter 1 
INTRODUCTION 
The development of the atomic bomb and the 
possible development of radiological warfare 
agents require that future military plans contain a 
certain emphasis on radiological defense. Instru- 
ments are a basic requirement in any such defense 
plan, since nature has not equipped man with 
senses capable of responding to nuclear radiations. 
Irreparable damage may be produced in high 
intensity fields which cannot be recognized with- 
out the use of suitable instruments. 
Since the first atomic bomb explosion, increas- 
ing emphasis and thought have been placed upon 
the development of instruments suitable tor mili- 
tary use. The instrumentation requirements are 
in many respects similar to those which have been 
encountered in X-ray radiographic and thera- 
peutic use, radium radiographic and therapeutic 
use, isotope research and therapeutic use, cosmic 
ray research, and investigations with high energy 
accelerators. Military instruments in general 
require, in addition, an ability to withstand rough 
usage under extreme weather, temperature, and 
geographic conditions. They should also be made 
as simple and foolproof as is possible within the 
limits of their detecting requirement. 
The field of radiological instrumentation, as it 
applies to the defense establishment, has been 
assigned the name “RADIAC”. This new word 
for the military vocabulary has been taken from 
the initial letters of—RAdiation, Detection, In- 
dication, And Computation. 
RESTRICTED 
1 Chapter 2 
RADIATION IN GENERAL 
2.01 Introduction 
Radiation, in the sense in which we are con- 
cerned, means nuclear emissions and is not 
concerned with the radiations which are manifest 
as radio waves, heat, and light (1) (2).* It is 
possible to separate these nuclear emissions into 
electrically charged and electrically neutral 
categories. 
The electrically charged radiation consists of 
particles in motion such as: 
beta (/3) particles (electrons—e~) 
alpha (a) particles (helium nuclei—He++) 
protons (p) (hydrogen nuclei) (no military 
importance) 
positron (positive electron) (no military 
importance) 
The electrically neutral radiation consists of: 
neutron (n) 
gamma rays (7) 
X-rays (not considered as a nuclear radiation) 
Except in a few unique applications, military 
consideration is given to the measurement of the 
charged alpha and beta particles and to the 
electrically neutral gamma rays. Of these radia- 
tions, the greatest emphasis is placed on measure- 
ment of gamma rays. Table I gives some rough 
comparisons of the characteristics of alpha and 
beta particles and gamma rays. 
The measurement of neutrons will become 
important in conjunction with the operation of 
nuclear reactors for power production or the 
propulsion of ships or aircraft. Detection of 
neutrons involves some specialized applications 
of the detecting principles which will be discussed. 
However, a detailed description of neutron detec- 
tion will be omitted, since neutrons at present are 
of limited interest to the Defense Establishment. 
It should be noted that there are certain 
elements which give off pure alpha and pure beta 
radiations. Gamma radiations are produced 
only as an after-effect of either an alpha or a beta 
emission. With very minor exceptions, there is 
no such thing as a pure gamma emitter, although 
in some cases the alpha or beta emissions may be 
so weak as to be virtually indetectable. 
Table I.—Characteristics of nuclear radiation 
Radiation 
Nature 
Energy 
Ionizing power in air 
Penetration 
Range in standard air 
Alpha Par- 
ticle 
Heavy positively 
charged particle. 
Helium nucleus 
He++. Velocity 0 
to 2 x 109 cm/sec. 
High 4 9 Mev** 
High 40,000-250,000 
ion pairs; 20,000- 
80,000 ion pairs 
per centimeter 
5.5Mev—4.0 6 x 
10~3 cm in Al- 
umium 
7 Mev—6.0 cm 
5 Mev—3.48 cm 
2.0 Mev—1.0 cm 
0.2 Mev—0.17 cm 
Beta Par- 
ticle 
Light negatively 
charged particle. 
Electron e-. Ve- 
locities up to 
99.7% that of 
light 
Up to Me- 
dium High, 
0-3 Mev 
Medium 30-300 ion 
pairs per centi- 
meter 
0.15 Mev—1.0 mm; 
2 Mev—3.5 mm 
in Aluminum 
0.2 Mev—37 cm 
2 Mev—840 cm 
Gamma Ray 
Electromagnetic ra- 
diation. Wave 
length from 5 x 
10-10 to 4 x lO-8 
cm. Uncharged 
Low to Me- 
dium High, 
0.03 - 2.6 
Mev 
Low 0+ 
Lower intensity 
expotcntially 
along its path 
Thickness to reduce 
intensity of 1 Mev 
to one-half: 
Air—350 feet 
Lead—0.9 cm 
♦*Mev=Million electron volts=amount of work done when one electron is accelerated by a potential difference of one million volts. 
•Numbers in parentheses indicate references on page 83 of this manual. 
3 RADIAC 
2.02 Electrically Neutral Radiation 
The fact that gamma (or X-rays) are uncharged 
means that it is not possible to detect them 
directly with present types of measuring equip- 
ment. Fortunately these radiations in their 
passage through matter produce secondary proc- 
esses which allow measurement. 
In order to understand the methods of measure- 
ment of gamma rays, it is necessary to consider 
the manner in which neutral radiation is absorbed. 
It can be shown that absorption, or attenuation, 
takes place by several processes, the most im- 
portant being the following: 
A. Photoelectric Effect 
As shown in figure 2a, an atom irradiated 
with gamma rays absorbs the radiation by ejecting 
an electron. This type of absorption is dependent 
on the absorbing medium, but as a rough rule, is 
only important with gamma rays having energies 
below 0.1 Mev." 
B. Compton Effect 
In some cases, photons of gamma radiation 
behave like billiard balls and produce the effect 
shown in figure 2b. Energy is absorbed from the 
incident photon to eject an electron. The scat- 
tered photon has, as a result, lower energy than 
the incident photon. This effect is important in 
the range of energies up to roughly 1 to 10 Mev. 
C. Pair Production 
With high energies above 1 Mev, pair produc- 
tion becomes possible, and becomes predominant 
in the region 5-12 Mev and above, being more 
important in absorbers of high atomic weight. 
Diagrammatically, this is shown in figure 2c where 
a high energy gamma photon is absorbed by pro- 
ducing a pair of electrons. As shown all three 
methods of absorption result in the production of 
high energy electrons which are electrically charged 
particles of the same general type as beta particles. 
It should be reemphasized that only if un- 
charged radiations are instrumental in producing 
charged radiations through some secondary proc- 
ess can they be detected or measured by the 
various means which will be discussed. 
2.03 Electrically Charged Radiation 
Several possibilities present themselves for the 
measurement of electrically charged particles. 
Methods employing gas ionization prove to be 
the most convenient and practical. When a 
charged particle enters a gas it may act on a 
neutral gas atom or molecule with sufficient 
energy to remove one or more electrons. This 
process is called ionization and results in a single 
neutral atom or molecule being split into two for 
more) electrically charged particles—the negative 
electron(s) and the positively charged remaining 
portion of the atom or molecule. The removal of 
a single electron produces what is called an ion 
pair. The energy required to produce ion pairs 
depends upon the particular gas involved. In the 
case of air, which is a mixture of gases, the average 
loss of energy by the electrically charged particle 
is about 32.5 electron volts for each ion pair pro- 
duced. This does not mean that 32.5 electron 
volts go into the formation of the ion pair. 
Actually, only about half of this value is used 
specifically to strip off the electron in an ionizing 
collision. The remainder of the 32.5 electron 
volts is given up in the excitation of gas molecules 
in inelastic collisions which do not produce ions 
or in providing kinetic energy to the members of 
Oamma photon being absorbed with the production of an electron pair. This 
only occurs in the vicinity of the nucleus. 
Figure 2. Gamma ray absorption. 
Three methods of gamma ray absorption are shown by 
means of schematic diagrams. It will be noted that a 
negative electron (e~) is produced by each method. 
4 RADIAC 
and ion pair if ionization is produced. We will 
discuss later the excitation phenomenon in con- 
nection with certain crystals, but for the moment 
ionization is of the greatest interest. 
In the process of ionization, particles having 
greater electrical charge will produce greater 
ionization. Also, the more massive particles 
moving with lower velocities will present longer 
periods of time in which forces can act and, as a 
result, will be more effective in producing ioniza- 
tion than less massive particles. As an example, 
the transit in air of the negatively charged beta 
particle will produce between 30 and 300 ion pairs 
per centimeter of path length with the higher 
ionization occurring for lower beta particle ener- 
gies. The heavier, doubly charged positive alpha 
particle will produce anywhere from 20,000 to 
80,000 ion pairs per centimeter of travel. 
The ion pairs produced in a gas by the transit 
of an electrically charged particle will recombine 
to form neutral molecules. In the case of air at 
atmospheric pressure the life of an ion pair is 
believed to be in the order of five minutes. If, 
prior to recombination, the particles are subjected 
to an electric field, they will move under the in- 
fluence of the field, the positive ions toward the 
negatively charged cathode, and the negative ions 
toward the positively charged anode. A gas filled 
chamber containing electrons which have sufficient 
strength to collect all of the initially formed charge 
is called an ionization chamber. The electric field 
strength required for charge collection in chambers 
generally is between 15 and 120 volts per centi- 
meter and usually is not critical. This voltage 
corresponds to the field necessary to collect the 
ions prior to appreciable recombination and is not 
high enough to produce additional ion pairs as the 
ions travel to the collecting electrodes. 
5 Chapter 3 
IONIZATION CHAMBER 
3.01 Introduction 
With appropriate forms of chambers all ionizing 
radiations can be detected (4). In the case of 
heavily ionizing radiations such as alpha particles 
(and in some cases electrons), separate ionizing 
events can be counted in a manner similar to that 
which will be described for Geiger-Mueller and 
proportional counters. Design characteristics of 
instruments are thoroughly entwined with opera- 
tional usage and the type of radiation involved. 
In general, the chambers are built around three 
basic forms: 
A. Two parallel electrode plates, one highly 
insulated and directly connected to the measuring 
part of the instrument. 
B. Cylindrical electrode with a coaxial collect- 
ing rod. 
C. Rectangular box with an internal collecting 
network (sometimes called a Christmas tree). In 
practice, form C is little more than an adaptation 
of the cylindrical condenser in B. 
The anode and cathode previously mentioned, 
may take the form of electrodes in a simple elec- 
troscope in which the chamber (container) forms 
one electrode and the central wire and thin gold 
foil form the other electrode as shown in figure 3. 
The electrostatic field produced by the positive 
charge on the central electrode and the negative 
charge on the case exerts a force on the charge 
on the gold leaves which causes the leaves to 
separate. Ions formed inside the chamber by 
radiation will neutralize the charge on the gold 
foil leaves, and the leaves will move together. 
Thus, within certain limits, it is possible to read 
radiation dose as a function of position of the 
sensitive element of an electroscope (3). An 
electroscope has no external voltage source, how- 
ever, if the instrument used for the measurement 
of the electric charge collected in an ionization 
chamber utilizes a continuous external voltage 
for its operation it is called an electrometer. 
3.02 Pocket Dosimeter 
A useful military instrument is the quartz fibre 
pocket dosimeter which is a modified version of the 
Lauritsen Electroscope (1). A dosimeter is pic- 
tured in figure 4. This instrument, about the 
size of a fountain pen, utilizes a metallic coated 
quartz fibre some five microns (0.0002 inch) in 
diameter as the sensitive moving element in place 
of the thin gold foil in our previous example. 
The instrument incorporates a small compound 
microscope for viewing the fibre against a cali- 
brated scale. Some type of light source must be 
available in order to see the scale and fibre. 
These dosimeters, having a full scale sensitivity 
0.2 roentgen (r),* are in common use for measur- 
ing integrated gamma ray exposures. Work is 
under way to produce pocket dosimeters having 
full scale readings, perhaps as high as 200 roent- 
gens. Pocket dosimeter reading and charging is 
shown in figures 5 and 6. 
Figure 3. Laboratory type electroscope. 
Separation of leaves is caused by the repulsive force 
between two like charges. 
*See page 52 for an exact definition of a roentgen. (This is a unit of measure- 
ment of gamma or X-ray dosage rate or absorption.) 
7 RADI AC 
A light source must be available to see the scale and 
fibre. Here a reading is made using sky light for il- 
lumination. 
in as a part of the instrument. Dosage rate is 
obtained by timing the rate of electroscope fibre 
movement. Timing is accomplished by the re- 
petitive flashes of a neon lamp which appears to 
the viewer just above the microscope scale. Since 
the instrument keeps its calibration over extended 
periods of time, it is used as a secondary standard. 
Figure 5. Reading the pocket dosimeter. 
Shown is the dosimeter with the magnetic charging de- 
vice recently developed by Dr. F. R. Shonka of the 
Argonne National Laboratory. A magnet in the charger 
repels the dosimeter magnet and moves it into position so 
that the electroscope can be charged. Many dosimeters 
incorporate diaphragm charging terminals such as that 
shown with the pocket chamber in figure 8. 
3.03 Drift Meter 
A medium sized portable gamma measuring, 
alpha and beta indicating, survey instrument has 
been built with a quartz fibre system similar to 
that used in the pocket dosimeter. In some areas 
this instrument goes under the name Landsverk 
Electroscope. The unit has an enlarged chamber 
and is designed for portable but not pocket use. 
Since it is not a pocket device the charger is built 
Figure 4- Pocket dosimeter. 
Figure 6. Charging a pocket dosimeter. 
8 RADIAC 
Thin windows in the bottom and end of the chamber case make possible the detection of beta and alpha radiations. 
Figure 7. Schematic drawing of quartz fibre survey instrument, 
The instrument can be made extremely rugged as 
a gamma reading instrument. The problems 
associated with thin windows necessary for alpha 
and beta admission to the chamber will be dis- 
cussed later. Figure 7 shows a type of commer- 
cially available drift meter. 
3.04 Pocket Chamber 
The charge on the chamber electrodes can be 
measured, and any decrease in charge over a 
period of time can be calibrated to give a measure 
of the radiation dose which has produced the charge 
decrease. For a number of years thimble chambers 
have been built to record X-ray dosages up to 
2500 roentgens for energies between 0.08 and 0.25 
Mev. 
The pocket chamber, figure 8, again about the 
size of a fountain pen, is an instrument utilizing 
this principle. Usually the instrument required 
to place the charge on the pocket chamber is used 
at some later time to read any decrease in charge. 
These instruments are more simply designed, and 
as a result, less costly than the pocket dosimeters 
($5 as compared to $40). They have a use in 
military operations where it is desired for one 
reason or another to prevent the wearer from 
knowing the dose he has received. A great num- 
ber of pocket chambers are in use which have a 
total sensitivity of 0.2 roentgen gamma exposure. 
Other pocket chambers are being constructed 
which have gamma sensitivities of 100 roentgens 
and there are considerations of chambers reading 
as high as 1000 roentgens. The wearing and reading 
of pocket chambers is shown in figures 9 and 10. 
3.05 Electrometers 
Metal coated quartz fibres mounted on a torsion 
fibre between electrodes are used as electrometers 
for ion detection. Several forms have been de- 
veloped which have found some use in the labora- 
tory measurement of alpha particles and low 
energy beta rays. The application of an external 
potential to the electrodes produces an instrument 
which is somewhat more sensitive than the elec- 
871748°—50—2 
9 RADIAC 
Figure 9. Wearing a pocket chamber. 
sible radiation dose (industrial tolerance level) 
for one day, an average current of 3 x 10~12 amperes 
would be produced. Such minute currents require 
the use of vacuum tube amplifiers and special 
handling techniques in order to make proper 
measurements. These special electronic circuits 
are known as electrometer circuits. 
3.06 Chamber Characteristics 
The characteristics of a particular radiation 
which enter into ionization chamber design are 
This is a non self-reading gamma dosage indicating 
device about the size of a fountain pen. 
Figure 8. Personnel pocket chamber. 
troscope. In most general use in this country are 
the Wulj and the Lindemann electrometers. How- 
ever, aside from possible laboratory usage the 
quartz fibre electrometer has little military appli- 
cation. 
If radiations are allowed to produce ions in the 
space between two electrodes, as shown in figure 
13, and an electric field is induced to pull the ions 
from the region in which they were created the 
positive ions will move toward the cathode 
(central wire), and the electrons which are 
produced at the same time will move in the 
opposite direction toward the anode (chamber 
case). Current will therefore flow in the circuit 
until all ions are collected. This ionization cur- 
rent is very small. In the case of a one-litre 
chamber having air under standard conditions of 
temperature and pressure the maximum permis- 
10 
Figure 10. Charging and reading the pocket chamber. RADIAC 
the size of the source to be measured, and the 
range of dose rate anticipated. The physical 
characteristics of the chamber which can be varied 
to meet various requirements are— 
1 Chamber Window 
2 Chamber Wall Material 
3 Pressure and Type of Chamber Gas 
4. Chamber Volume 
3.07 Chamber Window 
Gamma rays have penetrating powers which 
eliminate the requirements of admission windows. 
This is fortunate since the greatest number of 
military instruments will be gamma-reading, 
and it is much easier to make a fully packaged 
instrument rugged. This is not the case with 
either alpha or beta particles. Beta particles are 
characterized by a relatively low penetrating 
power. Beta particles having an energy of 2 Mev 
have a range of slightly greater than eight meters 
in standard air. With aluminum as the absorber, 
maximum beta penetrations are roughly as shown 
in table II. 
Table II.—Range of beta particles in aluminum 
Energy Mev Thickness 
mm mg/cm* 
0.15 0. 1 30 
0.5 0. 6 160 
1.0 1. 5 409 
2.0 3. 5 951 
4.0 7. 5 2,035 
It is customary in all types of nuclear work to meas- 
ure window thickness in mass per unit area 
(mg/cm2) since this gives a good practical unit of 
absorption that can be used for the measurement 
of very thin films. Those thicknesses indicate 
that there is only a moderate problem of getting 
beta particles into chambers for laboratory use. 
The problem of making chambers with beta 
windows capable of rough usage is another much 
more difficult problem. One form of alpha-beta- 
gamma portable ionization chamber survey meter 
is shown in figure 11. 
In the case of alpha particles there is consider- 
ably less penetration than with beta particles. A 
5 Mev alpha particle has a range of 3.5 centimeters 
in air; therefore, it is readily seen that there is a 
real problem in getting an alpha particle into a 
chamber. Few windows are sufficiently thin for 
Figuee 11. Alpha-heta-gamma portable ionization chamber survey meter. 
Because of the thin window, this instrument type has a doubtful future as a military instrument, 
11 RADI AC 
alpha admission. Thin mica and stretched nylon 
and rubber hydrochloride films about 5 microns 
thick and with a mass as low as 0.5 milligrams per 
square centimeter have been used with some suc- 
cess. However, even with these extremely thin 
films, the alpha particle will lose from one to two 
centimeters of range during its penetration. It 
becomes apparent that alpha chambers stand little 
chance of developing into instruments for field use. 
3.08 Wall Material 
The wall material is of little importance to 
chambers devoted to alpha and beta measure- 
ments; however, the wall material becomes serious 
with gamma-measuring chambers since the gamma 
ray measurement stems from its absorption in the 
interior face of the chamber wall. Through the 
mean gamma energies of 0.5 to 1.5 Mev the various 
mechanisms of absorption produce a fairly uniform 
secondary response. The process of photo-electric 
absorption becomes increasingly efficient for metals 
at lower energies, and a metallic chamber will give 
readings disproportionately high when subjected 
to low energy gamma rays. As a result, much 
effort is placed into coating the interior chamber 
walls with nonmetals of low atomic number and 
writing specifications: 
“ the chamber will be air equivalent 
and wave length independent to within ±20% 
from 80 Kev to 1.5 Mev quantum gamma 
radiation.” 
Since the ultimate usage of these instruments is 
for health protection, it is desirable to have the 
inner wall coating approach the absorption of 
human tissue. Tissue is composed primarily of 
the light elements—hydrogen, oxygen, nitrogen, 
and carbon. Chamber walls therefore are made of 
bakelite or plastic containing a high percentage of 
carbon atoms or coated on the interior with a 
layer of colloidal carbon. 
3.09 Pressure and Type of Chamber Gas 
The thin window’s required to admit alpha 
particles prohibit the use of any gas other than air 
and at any pressure other than that of the normal 
outside atmosphere. Little success has been 
found in any gas other than air for beta measure- 
ments. It should be pointed out that aircraft 
transportability and possible use in the air pre- 
cludes the possibility of hermetically sealing at 
normal atmospheric pressure ion chambers having 
thin windows. The minute currents to be dis- 
Figure 12. Ionization chambers. 
From left to right are the ionization chambers from (a) Victoreen 247A (IM-3/PD) cut open to show the chamber 
interior, collecting electrode, and electrometer circuit (top); (b) National Technical Laboratory MX-6 (IM-40/PD) 
cut open to show the collecting electrode system; (c) Victoreen Model 300 proteximeter (AN/PDR-2) broken open 
with only the anode showing; (d) Kelley-Koett manufactured AN/PDR-T-1 in which the sensitive electrometer 
circuit is housed in a compartment adjacent to the collecting chamber. This compartment is above the chamber in 
the illustration. 
12 RADIAC 
cussed in subsequent sections indicate the necessity 
of maintaining high insulation between electrodes; 
therefore, any breather holes, to maintain equilib- 
rium between internal and external pressure, must 
contain drying compounds to prevent moisture 
from entering the chamber. 
In the case of an ionization chamber for gamma 
measurement, there is some point to using a gas 
other than air at perhaps some elevated pressure 
in order to increase the effective gas cross section 
and increase the chamber sensitivity. Freon 12 
and argon have been employed in the chambers 
of portable instruments. 
3.10 Chamber Volume 
An increase in sensitivity is provided by an 
increase in chamber volume; however, with the 
majority of portable survey instruments, the 
operational desires are for smaller, more compact 
equipments. Three chambers from different por- 
table survey instruments and one chamber from 
a group dosimeter are shown in figure 12, The 
physical size and shape of insulators are all that limit 
the smaller sizes of chambers. Large chambers are 
limited by the high voltage required to insure ion 
collection. Any type of corona discharge as the 
result of high voltage will produce ions which will 
give spurious readings. 
3.11 Electronic Characteristics 
The simplest arrangements consist of a central 
collecting probe through the center of the chamber 
as one electrode and the interior of the chamber 
case as the other electrode with a battery con- 
nected across the two. Under normal ionization 
chamber usage the negative terminal of the battery 
is attached to the central probe, and the positive 
terminal to the chamber wall (note that the 
reverse is true for proportional and Geiger counters). 
With the arrangement as shown in figure 13, it is 
possible to determine the voltage across the resistor 
R. Knowing the volume of the chamber, current 
flow can be calculated, since a radiation dose rate 
of one roentgen per hour causes a current flow of 
9.28X10~14 amperes per cubic centimeter of cham- 
ber gas volume. For example, if we consider a 
relatively large chamber having a volume of one 
litre and an extremely high resistance for R of 
1011 ohms; then a current flow of 9X 10~n amperes 
will cause a voltage across R of 9 volts per r/hr. 
This value is sufficiently high to be of some value. 
In practice, the voltage is not utilized directly, 
Figure 13. Ionization chamber circuit. 
since it is not possible to make measurements 
across resistors having values of the order of mag- 
nitude of 1011 ohms In addition, if our example 
were taken in the range of daily tolerance intensi- 
ties, say 4 milliroentgen per hour (0.004 r/hr), the 
potential drop across R would be 0.037 volts. 
Vacuum tubes therefore are required as a means 
of amplifying voltage and currents of this order of 
magnitude. 
The common types of vacuum tubes have been 
rejected for ionization current amplifiers. The 
normal tubes have an extremely small flow of cur- 
rent from grid to cathode, known as the grid cur- 
rent, which may be of the order of magnitude of 
10“9 amperes. However, 10~9 amperes when al- 
lowed to flow through a resistance of 1011 ohms will 
produce a potential drop of some 100 volts. Elec- 
trometer tubes, specifically designed with grid cur- 
rents of 10~15 amperes or less are being manufac- 
tured for use in ionization chamber instruments. 
Low grid currents are obtained by operating the 
tubes at low filament temperature and by placing 
screen grids between the filament and control grid. 
These screens are at a very slight positive poten- 
tial so as to collect the electrons normally surround- 
ing the cathode. A group of electrometer tubes 
are shown in figure 14. 
In addition to the low grid current characteris- 
tics, the electrometer tubes are designed to insure 
extremely low leakage currents. These currents 
are held to a minimum by operating the tube at 
low plate voltage and current. Extreme care 
must be taken in the handling of electrometer 
tubes, since body oils deposited on or near the tube 
base may cause serious leakage currents. 
Special manufacturing techniques also are re- 
quired to produce resistors up to 1014 ohms. Five 
such resistors, carefully sealed in glass, are shown 
in figure 15. 
13 RADIAC 
Figure 14- Electrometer tubes. 
Shown is an assortment of subminiature triode, tetrode, and pentode electrometer tubes which are used for 
the amplification of the minute currents produced by radiation in ionization chambers. 
Figure 15. Resistors for electrometer circuits. 
Shown is an assortment of resistors having values of 108 to 10u ohms. The resistor is inclosed in a glass envelope 
1% inches long and 0.2 inches in diameter. 
3.12 Ionization Chamber Instruments 
Radiac instruments, sensitive to gamma radi- 
ations, with 30 to 50 cubic inch chambers are 
useful as light weight, high dose rate measuring 
instruments for field survey work. Such an 
instrument is shown in use in figure 16, and dia- 
gramatically in figure 17. This is perhaps the 
most important of all military radiation survey 
instruments. Thin window survey chambers as 
previously discussed in connection with figure 11 
may be used to measure gamma radiation and 
give indications of alpha and beta radiations. 
Ionization chambers have many uses such as in 
the small pocket dosimeters and chambers for 
individual dosage measurements and with larger 
chambers for group dosage recording devices. 
Figure 16. An ionization chamber survey meter goes ashore 
during landing maneuvers. 
14 Chapter 4 
GAS AMPLIFICATION 
Ionization chamber voltages are relatively weak. 
However, if higher voltages are applied to the 
chamber electrodes, a gas amplification can be 
obtained (5). When the electron from an ion pair 
is given greater energy than the ionization energy 
of the atom or molecule of a gas, it may produce 
additional ionization as shown diagramatically in 
figure 18. Gas amplification also can be obtained 
by reducing the energy required to ionize the 
chamber gas through the choice of a suitable gas 
or by decreasing the chamber pressure so as to 
increase the mean free path and the energy of the 
ionizing particle. 
If we consider the counting chamber and cir- 
cuitry as shown in figure 19 with the chamber 
exposed to a constant energy source of radiation, 
each particle entering the chamber will produce a 
definite number of ion pairs, and these ions will 
be collected at the electrodes, thereby producing 
a pulse of current in the external circuit. 
If the size of the pulse is plotted as a function of 
the voltage applied to the electrodes, a curve such 
as that shown in figure 20 is formed. 
Below a certain minimum voltage across the 
chamber we do not collect all the ions which are 
formed, because in this region of low voltage, 0~a, 
ions have an opportunity for recombination prior 
to collection. At slightly increased voltages, a-b, 
normal ionization chamber working conditions are 
reached. Above voltage a the pulse size becomes 
relatively independent of the voltage, since there 
is a complete collection of all ions formed by the 
Figure 17. Ionization chamber survey meter. 
Gamma-measuring instruments of this type are probably the most important military survey instruments, 
15 RADI AC 
Figure 18. Gas amplification. 
Diagramatic representation of the avalanche type of gas amplification found throughout the Geiger-Mueller 
tube and near the collecting electrode of a proportional counter. One initial ionizing event may produce 103 
electrons collected in a proportional counter and 108 electrons collected in a Geiger-tube. 
where: 
N = Number of ions collected 
c = Charge on the electron (coulombs) 
q = Capacity of the system (farads) 
If we assume the capacity of the system to be 10-11 
farads and examine the voltage produced by 1 
centimeter of travel of a 1 Mev alpha particle, 
then: 
Figure 19. Counting chamber and circuit. 
passage of an ionizing particle. In the region 
O-a-b, only ions produced by the primary radiation 
contribute to the pulse. In the region a-b the 
pulse P in volts will be given by the relationship: 
P=Xc 
q 
p= (4 X lO-.1-8)=6.4 x 10-4 volts 
16 RADIAC 
The same length of travel with a 1 Mev beta 
particle: 
p==(30)(h6X10 19)=4 8X1Q—7 volts 
One would expect a slightly larger voltage, say 
4 x 10~7 volts to be produced as the result of the 
secondary electron produced in the absorption of 
a 1 Mev gamma ray. Assuming photoelectric 
absorption of the gamma ray, some energy is 
required for ’ionization, some energy will perhaps 
go into kinetic energy of the products of ionization, 
and there may be some excitation of other elec- 
trons in the ionized atom. At any rate, it would be 
expected that the photoelectron would be produced 
with very slightly less energy than the 1 Mev beta 
particle and because of its lower velocity (see 
page 4) will produce a slightly greater number 
of ion pairs per centimeter of travel in the 
chamber. If the chamber is such as will expend 
all the energy of the beta particle or photoelectron, 
the total number of ion pairs produced by the 
beta particle will be slightly in excess of those 
produced by the gamma ray photoelectron. 
Figure 20. Pulse size as a function of voltage from a cham- 
ber exposed to a constant energy source of radiation. 
a-b Ionization chamber region 
5-c Proportional region 
c-d Limited proportional region 
d-e Geiger region 
above e Continuous discharge region 
17 Chapter 5 
PROPORTIONAL COUNTER 
5.01 The Proportional Region 
At some higher voltage b in figure 20 the above 
relationship would cease to exist, and pulses would 
be found larger than predicted. The region b-c is 
the so-called proportional region, because the out- 
put pulse is directly proportional to the amount of 
primary ionization. The chamber operation in the 
proportional region can be explained as follows: 
In the region of a few electron mean free paths 
away from the central (anode) wire, a sufficiently 
high field strength imparts to electrons, attracted 
from the remaining chamber volume, enough 
energy to cause secondary ionization. The output 
pulse is therefore increased by the collection of 
the additional electrons and is proportional to the 
magnitude of the initial ionizing radiation. 
If there are I ion pairs formed by collections as 
an electron travels toward the central electrode, 
then the size of the voltage pulse is given by— 
we are able, within limits, to differentiate between 
the pulses produced by alpha particles and the 
pulses produced by either beta or gamma radia- 
tions. This means that the proportional counter 
will have a limited military usage for alpha meas- 
urements. If the field strength is such as to form 
a beta-gamma to alpha ratio of 105 or greater, 
such as roughly approximates the case immedi- 
ately following an atomic bomb explosion, the 
proportional counter is not capable of differen- 
tiating between the combined effects of a multi- 
tude of smaller beta and gamma pulses and the 
large alpha pulses. The proportional counter 
has a definite use in decontamination work after 
the decay of the short half-life gamma and beta 
emitters. A portable proportional counter survey 
meter is sketched in figure 21, 
Certain factors must be considered in order to 
establish good working characteristics for propor- 
tional counters. The gas used for tube filling may 
be chosen so as to accomplish the desired action. 
Pure argon, helium, neon and methane, and cer- 
tain combinations of these gases have been found 
to give satisfactory results. Other counter probes 
are left open to the air. Strong electric fields 
may be produced with moderate voltage by using 
two coaxial cylinders as the electrodes, and since 
the field strength varies logarithmically for a 
cylindrical configuration, the smaller the diameter 
of the anode, the higher will be the field strength 
in the vicinity of one electron mean free path of 
the wire. For this reason, extremely fine central 
electrode wires are employed. It is readily seen 
that the mechanical strength of a thin window 
tube with a 0.0005 inch diameter central wire is 
not such as to lend itself readily to field use. 
5.02 Proportional Counter Probe 
As previously stated, a counter for use in the 
proportional counter region is restricted in the 
multiplication of electrons to somewhere in the 
order of ten generations. This can be obtained 
in the large electric field near the central wire in 
the cylindrical arrangement described above. It 
follows that a parallel plate structure is excluded 
r_(I)(1.6X10-19) 
q 
Here, “I” is defined as the gas amplification and 
is the ratio of the number of electrons collected at 
the anode N to the number of ion pairs originally 
formed in the gas N0: 
!_N 
1 N. 
It should be noted that the gas amplification fac- 
tor varies from about 10 in certain photoelectric 
cells to 103 in proportional counters and to 108 in 
some Geiger-Mueller counter tubes as shown in 
the diagram in figure 18. 
In the case of the proportional counter it is 
necessary that the secondary ionization (or am- 
plification) occur less than ten electron mean free 
paths from the central wire. Otherwise strict 
proportionality ceases, and the limited propor- 
tional region c-d is entered where the gas amplifi- 
cation factor has values from 104 to 107. 
Since the total ionization produced by an ion- 
izing particle is dependent on the type of particle, 
it follows that in the proportional counter region 
19 Figure 21. Portable proportional counter survey meter. 
This type of instrument will be used for alpha particle detection. 
for use in a proportional counter. It is possible 
to build proportional counter probes with large 
windows using a number of parallel wires. A 
satisfactory geometrical configuration lias been 
found where the depth of the chamber behind the 
window is “x”, the wires are placed at a depth 
“x/2” and a distance “x” apart. In some probes, 
“x” has been chosen equal to one centimeter. 
Such a multiple wire probe is shown in figure 22. 
A single wire probe is shown in figure 21. In this 
latter example the probe case is not completely 
cylindrical since the window opening is cut longi- 
tudinally along the side wall. 
Parallel wire counters having large sensitive 
openings (100—150 cm2) are used for the survey of 
large areas. Proportional counters with probes 
are used for checking alpha contamination on 
A satisfactory geometrical arrangement has been found 
with x = 1 inch. 
Figure 22. Parallel wire proportional probe. 
hands, feet, clothing, filter paper samples, and 
various surfaces. This is primarily a tool used in 
conjunction with a field laboratory and with 
decontamination activities. 
20 Chapter 6 
GEIGER-MUELLER COUNTER 
6.01 Avalanche Ionization 
If in our previous example (fig. 20) the voltage 
is raised still further above point c the gas amplifi- 
cation factor will continue to increase, but in the 
region c-d, the amplified pulses are no longer 
proportional to the initial ionization. This means 
that secondary ionization is started outside the 
distance of a few electron mean free paths from 
the central wire. There is still some difference in 
final pulse sizes so that this region c-d is known as 
the region of limited proportionality. Tubes oper- 
ated in this region have little application outside 
research laboratories. 
If the voltage is increased still further, a new 
phenomenon occurs in which secondary ion 
multiplication spreads throughout the entire 
chamber volume. This cumulative effect is known 
as Townsend or avalanche ionization and is shown 
diagrammatically in figure 18. When a chamber is 
used in this region d-e, it is called a Geiger-Mueller 
counter, and the pulse size is independent of the 
event which initiated it. Still higher voltages 
produce above point e a region of continuous arc 
discharge. While in effect this is not a continuous 
discharge but a series of pulses so closely spaced 
to give that appearance. 
It should be noted that for any particular 
counter tube, if the pressure is held constant and 
the voltage is varied the instrument can be made 
to operate as either an ionization chamber, pro- 
portional counter, or Geiger counter. By holding 
the voltage constant a similar situation can bo 
created by varying the mean free path through 
variations in gas pressure. 
An examination of pulses from a Geiger-Mueller 
tube reveals that pulses are of the same size only 
when spaced a good time apart. One would 
expect all pulses to be of the same size, but an 
examination of the action of the positive ion 
reveals that this is not always the case. In 
previous discussions of the operation of ionization 
chambers and proportional counters we have 
neglected the effect of the positive ions and con- 
sidered onlv the action of the electrons. Because 
Figure 23. Geiger-Mueller tube pulse. 
After one pulse has started at w, no second event can 
take place until the pulse reaches y. The time w-y is 
the tube dead time. 
of their mass, the positive ions move slowly under 
the influence of the electric field reaching the 
outer collecting electrode in perhaps 10“3 seconds. 
The electrons formed during the Townsend 
avalanche, being many orders of magnitude (104) 
lighter, are all collected in less than 10~6 seconds, 
which is a long time before the positive ions reach 
the cathode. The result is a cloud of positive ions 
forming at a distance of several mean free paths 
from the anode and moving toward the cathode. 
This produces a positive space charge which for a 
time completely shields the anode and prevents 
counter action. As the positive charge moves 
closer to the cathode, a limited counter action is 
allowed to occur. In this case the initial pulse 
will be of greater magnitude than that of the one 
which follows. An examination of the pulse 
delivered by a Geiger-Mueller tube may be made 
with the help of figure 23. 
The pulse develops rapidly from w to x, due to 
the rapid collection of electrons. The pulse 
decays more slowly from x to z, due to the longer 
transit time of the positive ions and the time 
constant of the external circuit. After one pulse 
has started at time w, no second event can take 
21 RADIAC 
place until the pulse has reached y, due to the 
shielding action of the positive space charge. 
The time w-y, in which no second event can take 
place, is called the tube dead time. This time 
is very important, because it determines the 
maximum counting rate of the tube and its allied 
circuit. In portable survey instruments the dead 
time is approximately 0.0005 second which allows 
a maximum counting rate of 2,000 pulses per 
second. It becomes apparent that since the 
maximum tube response is Vaq then pulses 
occurring after time y will have a minimum ampli- 
tude of Yx-Yy. This amplitude will increase 
with time to Yx at time 2. Therefore, during the 
time of pulse decay starting with the end of the 
dead period, there will be a period y to z with 
pulses less than normal height. 
If we assume a Geiger-Mueller tube to be 
exposed to a constant intensity source having a 
wide spectrum of energies of gamma photons or 
beta particles; then a typical Geiger-Mueller 
tube characteristic curve of pulses per second as a 
function of voltage may be plotted in figure 24. 
region o-p is reached, and within the resolving 
time of the tube practically every particle entering 
the tube which is capable of producing at least 
one ion pair in the tube gas is counted. Beta 
particles which penetrate the tube walls will be 
counted with almost 100% efficiency; on the 
other hand, gamma rays must produce ionization 
in the tube in order to be counted. The gamma 
counting efficiency usually is considered less than 
one per cent. The region of continuous discharge 
begins at p. 
The Geiger portion of the characteristic curve 
o-p is known as the plateau. It is desirable, 
particularly in portable battery operated survey 
meters, to have a long, flat plateau; since the 
counting rate does not depend on applied voltage 
and, within limits, will not be affected by battery 
aging. Tubes having plateau lengths from 100 to 
300 volts and slopes showing an increase in counts 
of only one to two per cent for a change of 100 
volts are in general usage. In many portable 
survey instruments these tubes operate with the 
threshold of the Geiger region in the neighborhood 
of 900 volts. In the laboratory equipment various 
tubes operate up to 2500 volts. Most of the 
portable radiac instruments are necessarily re- 
stricted to batteries, and the higher the voltage, 
the larger and heavier the battery requirements. 
Efforts are under way to develop satisfactory high 
voltage supplies* which operate from low voltage 
batteries. This is only a temporary expedient 
until satisfactory low voltage Geiger-Mueller 
tubes are developed. Constant voltage power 
supplies will reduce the requirement for a long 
plateau although tube aging with use many times 
causes voltage shifts in the characteristic curve 
which makes the plateau desirable. 
6.02 Quenching the Discharge 
The approach of the positive ion cloud to the 
cathode cylinder will result in pulling electrons 
from the cathode to produce neutral atoms or 
molecules. The electron usually enters combina- 
tion with the positive ion in an excited state. 
The process of transit to the ground state pro- 
duces a characteristic series of spectral radiation, 
and some of these radiations will be in the ultra- 
Figure 24. Geiger-Mueller tube characteristic curve. 
m Curve threshold 
m-n Region of proportional counting 
o Threshold of Geiger region 
o-p Plateau 
p Start of continuous discharge region 
There will be no response to the small pulses 
in the ionization chamber region where there is no 
gas amplification. A threshold m appears early 
in the proportional region. This region extends 
from m to n. As the voltage is increased, the 
gas amplification becomes increasingly more im- 
portant with more of the less energetic particles 
being counted. At o the threshold of the Geiger 
*There are essentially nine different types of power supply which can be 
used to provide the high voltage required for Geiger counter operation; 
Battery, condenser, condenser-commutator, vibrator, condenser-vibrator, 
radio frequency, fly-back, transformer (AC supply), and multiplier (AO 
supply). RAD1AC 
violet region. This ultra-violet radiation usually 
has sufficient energy to produce photoelectron 
emission from the cathode. These photoelectrons, 
in turn, will have sufficient energy to start a second 
avalanche, and the whole process will be repeated. 
It is therefore necessary to construct counters in 
which the cycle is halted for each individual pulse. 
This process is called quenching and can be ac- 
complished by using external electronic methods 
or by using special vapors inside of the counter 
tube. 
All external quenching methods work on the 
principle of lowering the collecting electrode 
voltage below that at which the counter can form 
an avalanche until such time as the danger of an 
additional avalanche is passed (3) (5). The 
recovery time for resistance quenched circuits is 
in the order of 10~2 seconds. The Neher-Harper 
circuit, a good example of vacuum tube quenching, 
is shown in figure 25. This circuit has a recovery 
time in the order of 10“4 seconds. 
When current flows as the result of a discharge 
of the detector, the resistor Ri raises the vacuum 
Figure 25. Neher-Harper vacuum tube quench circuit. 
tube grid potential. As the grid becomes positive 
from its normal —4.5 volt bias, the tube conducts, 
thereby dropping the potential on the collecting 
electrode. Other quench circuits in use are the 
Neher-Pickering, Getting multivibrator, and a 
number of combinations and variations. 
Internally quenched Geiger-Mueller tubes utilize 
small amounts of polyatomic vapor such as ethyl 
ether, amyl acetate, ethyl alcohol, etc., mixed with 
the regular tube gas in order to cause the detector 
Figure 26. Tubes for portable Geiger-Mueller counters. 
The diagram indicates the difference between thin wall and thin end window tubes. The Victoreen all metal thy- 
rode 1B85 is shown in the lower left. The thin-end window tube is the BS-1 used for beta-gamma indication in 
the AN/PDR-8 series, -15 and -27. The BS-2 for high range gamma detection in the same instruments is 
shown in the lower right. An assortment of thin-walled tubes from other portable counters is shown. 
23 RADI AC 
to quench itself after each discharge. These 
Geiger-Mueller tubes are known as self-quenching. 
The primary function of the vapor molecules is 
the absorption of ultra-violet photons, thereby 
forestalling any repetitive discharge. The major- 
ity of the quenching gases are complex organic 
molecules such as alcohol or xylene which preclude 
their use under subzero weather conditions. They 
also may show changes in sensitivity with changes 
in temperature at room conditions. One of the 
most severe problems presented by the quench 
vapor is in limiting the life of the tube. Some of 
the quenching vapor is dissociated at each dis- 
charge, and eventually the vapor is completely 
used up and the tube goes into a repetitive dis- 
charge condition. The better tubes in survey 
equipment will have a life of 3 x 109 counts. For 
continuous operation in a field which will just 
allow utilizing a 10“4 second resolving time, the 
tube life will be only 100 hours. 
Considerable work is under way toward the 
development of Geiger-Mueller tube fillings which 
will overcome the difficulties that have been 
enumerated above. Halogen gas mixtures are 
among the most promising. Tubes have been 
constructed with the Geiger threshold in the 
neighborhood of 700 volts, having a virtually 
flat plateau of several hundred volts. These 
tubes appear to have good temperature charac- 
teristics and a life well in excess of that for tubes 
generally employed in survey equipment. 
The majority of Geiger-Mueller counter tubes 
presently employed in survey meters are % inch in 
diameter and 5% inches long. The cathodes vary 
from one to three inches in length. In common 
use are thin side walls of 30 mg/cm2 thickness. 
Others have thin end windows in some cases 3 
mg/cm2 thick. Such tubes are shown in figure 26. 
Laboratory counter tubes range up to 3L inches 
in diameter with the length from two to ten times 
the diameter. Several laboratory Geiger-Mueller 
tubes are shown in figure 27. The anode, thor- 
oughly insulated from the cathode, is a fine wire 
from 0.0001 to 0.0010 inch in diameter running 
down the cathode cylinder axis. To obtain a 
satisfactory characteristic curve, the central wire 
must be manufactured carefully, free of die marks 
and sharp protuberances. The tube must be 
cleaned carefully to remove all dust, grease, water 
vapor, and oxygen; and special care must be 
exercised in the selection of pure filling gases. 
In addition, the filling gas pressure must be 
chosen carefully. Most tubes used in radiac 
equipment of the portable survey type incorporate 
thin windows to permit some beta counting. 
Normally, this is a cylindrical section of tube wall 
approximately 2 inches long at mid-tube length 
as shown in figure 26 and having a thickness of 30 
mg/cm2. Provided the probe housing tube does 
not add additional shielding, the tube then will 
be sensitive to beta particles having energies 
above 0.16 Mev. As previously stated, counter 
tubes may be employed with thin end windows 
such as that illustrated in figure 26. Tubes of this 
type of construction are in more common use in 
laboratory equipment than in equipment used for 
field survey work. Mica windows down to 0.5 
mg/cm2 are available, although in normal labora- 
tory work the thin windows run between 1.5 and 
4 mg/cm2 in thickness. 
Figure 27. Laboratory Geiger tubes. 
A number of tubes have been developed to cover the wide range of requirements of laboratory counting. 
24 RADIAC 
A great majority of Geiger-Mueller tubes are 
photosensitive. This undesirable feature has been 
overcome by coating the glass envelope with an 
opaque surface. Occasionally, pin holes in the 
thin opaque coating will cause spurious counts 
when the tube is exposed to bright sunlight. In 
addition, the opaque coating has been known to 
peel off a once satisfactorily operating tube and 
introduce serious counting errors. 
6.03 Portable Geiger-Mueller Detector 
Geiger-Mueller counters, utilizing self-quench- 
ing tubes, are especially useful as light weight 
highly sensitive detecting instruments for field 
Figure 28. Diagramatic sketch of a portable Geiger-Mueller survey meter. 
The probe, foreground, has a descriminating slide which may be used for beta indications. Indication is by 
the meter and by headphones (not shown). 
871748°—30 3 
25 RADI AC 
survey and decontamination work. Such an in- 
strument is shown in figure 28. The pulses are 
of such magnitude that they can be heard in 
earphones without the necessity of much external 
amplification. At low intensity levels, a few 
multiples of ordinary background (30-50 counts 
per minute—roughly 0.01 mr/hr) aural indications 
are found in many cases to be more useful than 
observation of an indicating meter. The majority 
of field instruments place the counter tube in a 
probe at the end of a three- to five-foot length of 
cable so that the larger, heavier case containing 
power supply electronic circuitry, meter, etc., can 
be held in one hand or by a shoulder strap while 
a detailed examination is made with the probe 
held in the other hand. A jish-pole type of ex- 
tended handle, which has been utilized with certain 
instruments to hold the probe at a distance from 
the operator’s body, is shown in figure 29. 
Figure 29. Geiger-Mueller counter in use. 
A fish-pole type of extended handle has been utilized 
with the AN/PDR-8 to hold the tube probe at a distance 
from the operator’s body. 
26 Chapter 7 
SCALING CIRCUITS 
Field laboratories will be used to evaluate 
samples of terrain, food, water, etc., to determine 
the nature and extent of radiological hazards. 
This work requires that accurate counts be made. 
The best mechanical counters can be driven at 
rates of perphaps no more than 300 times per 
second; therefore, other means are required to 
record the maximum Geiger-Mueller count in the 
neighborhood of 5,000 pulses per second. Elec- 
tronically, it is possible to record pulses at rates 
far in excess of the best counter tube output. 
Some of these electronic arrangements are known 
as scaling circuits. 
Scaling circuits are based upon a basic two- 
tube circuit which divides the number of pulses 
by two, and by constructing a series of such 
circuits, the pulses can be reduced by factors 
of 2, 4, 8, 16, 32, 64, 128, etc. The most common 
scaling circuits in use utilize scales of 64. Record- 
ing is accomplished by neon indicator lamps at 
each stage multiple of the circuit. The sum of all 
indicator lamps will give the number of pulses 
counted. Since 64 or more counts per second are 
not uncommon, the circuit is set to drive a me- 
chanical register which records the total number 
of 64 counts which have taken place. A greatly 
simplified scale of two scaling circuits is shown in 
figure 30. Essentially, the two plates are joined 
by a relatively large capacitor Ci of the order of 
0.1 ufd. The two cathodes are tied together 
through the identical resistors Hi and R2 and held 
at some small negative bias. Because of the cross 
coupling by capacitor Ci, the circuit will be in 
equilibrium when either tube is cut off and the 
other at maximum plate current. An impulse 
having fired Ti causes the grid of T2 to go negative 
with respect to the cathode and not fire. How- 
ever, the arrival of a second impulse gives a mo- 
mentary positive bias to the grid of T2 and 
accordingly it fires. 
Certain difficulties are inherent in translating 
powers of 2 into multiples of 10; therefore, elec- 
tronic circuitry is being devised to give readings 
of decades (units of 10), and all military field labo- 
ratory equipment will probably be so constructed. 
Scaling circuits can be used in conjunction with 
any type of pulse detection. Many instruments 
are constructed with high voltage power supplies 
Figure 30. Simplified scale of two scaling circuit. 
27 RADIAC 
which may be varied for proportional or Geiger 
counter action. Scalers are built with special 
parallel plate chambers for alpha counting, and 
with proportional counters having a continuous 
flow methane atmosphere for counting alpha 
particles in the presence of high beta and gamma 
activity. 
Occasionally in specialized fields of research 
such as the investigations of cosmic rays one may 
wish to record a count only when two or more 
tubes are discharged simultaneously or when one 
tube of a set does not discharge. Many circuits 
have been devised to provide the required dis- 
crimination and are known as coincidence and 
anticoincidence circuits. These circuits have re- 
ceived considerable description in technical litera- 
ture but have little potential use in military 
radiological defense and are mentioned to assist 
the reader with terminology. 
28 Chapter 8 
COUNT RATE METER 
The normal portable Geiger-Mueller survey 
meter uses a count-rate meter in addition to aural 
indication of pulses. This meter simply reads the 
rate of arrival of pulses and with rates above ten 
times normal background the rate is rapid enough 
so that a steady meter reading is obtained. In 
laboratory equipment it frequently is convenient 
to use a count-rate meter in place of a scaling cir- 
cuit. Considerable effort is placed in circuitry to 
provide the meter with pulses of the same size so 
that all pulses give identical contributions to the 
meter reading. 
Count-rate meters can be used to indicate the 
rate of arrival of almost any type of pulse. Many 
laboratory instruments are constructed with varia- 
ble voltage supplies that may be used with count- 
ing chambers, proportional counters, or Geiger 
counters. The laboratory count-rate meters 
usually are provided with terminals so that the 
counting rate may be fed into some type of moving 
paper recorder. In this manner sample decay 
characteristics may be obtained by recordings 
made over a period of time. 
External quenching methods, such as the Neher- 
Harper circuit previously discussed in connection 
with figure 25, can be employed in conjunction 
with laboratory scalers and count-rate meters. 
Space and weight considerations prohibit the use 
of external quenching circuits with portable equip- 
ment. Objections to use with portable equipment 
may, in the future, be overcome by the use of 
miniaturized circuits. 
29 Chapter 9 
CRYSTAL AND CHEMICAL DETECTION 
9.01 Excitation 
As previously shown, an electrically charged 
particle in its passage through a gas may come 
close enough to an atom to exert sufficient force 
to remove an electron and ionize the atom. In 
many cases the charged particle will not exert 
enough energy to cause ionization, but will cause 
one or more of the atom’s electrons to be raised 
to higher energy levels. The excited atom in 
returning to its ground state will radiate a char- 
acteristic series of spectral lines. Some liquids 
or solids subjected to ionizing radiation may give 
off a characteristic fluorescence which can be 
measured. In addition, the free electrons pro- 
duced in a solid or liquid by ionization may cause 
changes in the electrical conduction of the sub- 
stance in which they are produced. This latter 
process is sometimes referred to as photo conduction. 
Some crystals do not return immediately to a 
ground state after being exposed to radiation. 
This may manifest itself in a crystal color change. 
In some cases shining light on the crystal will 
release energy which has been trapped in the 
crystal excited stage. Some crystals will en- 
counter an effective change in electrical resistance 
when subjected to ionizing radiation. In some 
cases chemical reactions which produce color 
changes are initiated by the disassociation of 
compounds, formation of free radicals or electron 
attachments under the influence of radiation. 
With the exception of photographic film badges, 
which will be discussed later, these various phe- 
nomena are of interest only in that some day they 
may be incorporated into a military dosage meas- 
uring device. Much developmental effort is being 
placed on a dosage indicating tag which will 
change colors at various levels of exposure so as 
to be used for rapid determination of the degree 
of field exposure. 
9.02 Chemical Dosimeters 
It appears possible to detect nuclear radiations 
by methods depending upon chemical change 
induced by radiations. Detection of radiation 
by chemical reactions possesses a possible advan- 
tage over detection by other methods of instru- 
mentation, in that a single chemical method may 
be used to detect radiation over a wide range of 
intensity from a fraction of a roentgen to over 
1,000 roentgens. The problem involved in such 
a method of detection is that of finding and con- 
trolling a chemical chain reaction capable of multi- 
plying the radiation effect on a single molecule. 
The special requirements are that the nuclear 
radiation initiate a minimum chain length approxi- 
mately 105 for visual perception and that it not 
be initiated significantly by thermal radiation at 
ordinary temperatures. Five possible ways in 
which multiplication may be achieved are; 
A. Development reaction such as photo- 
graphic development. 
B. Explosive reactions such as benzoyl per- 
oxide triggered by nuclear radiation. 
C. Initiation of a free radical chain. 
D. Psychological, such as a color reaction. 
E. Thermoluminescence. 
A few examples of many proposed systems 
for accomplishing the above multiplication are 
indicated below. 
Phosphors. The development of a dosage 
indicating device in which a phosphor screen is 
combined with a photo-sensitive layer. The 
phosphor absorbs the high energy photons to 
which the photo-chemical layer is nearly trans- 
parent with the phosphor emitting an extremely 
large number of photons of ultra-violet light for 
each high energy photon absorbed. The photo- 
chemical layer absorbs the ultra-violet emission 
and in turn may be direct reading in shades of 
grey or in colors after a development process. 
This is an effective way to transform high energy 
radiation into a detectable form. 
Colored Dyes. The formation of colored 
dyes on exposure to radiation of luecocyanides 
with pararosaniline. 
Halogenated Compounds. The radiation 
decomposition of halogenated compounds can be 
used to produce color reactions. 
Pyridine Ring. The splitting and coupling 
of the pyridine ring under the influence of ionizing 
radiation may form colored compounds. 
31 RADIAC 
found that thio-Michler’s ketone can be used as a 
sensitive indicator for this reaction since it forms 
deeply colored complexes with cuprous (Cu+) but 
not with cupric (Cu++) salts. 
Reduction oj Molyhdic Acid. Molybdic 
acid (H2Mo04) is reduced slowly to a blue com- 
pound, molybdic blue (Mo205.rzMo03) on irradia- 
tion. Much greater sensitivity is obtained if an 
organic acid such as lactic acid is present. 
Reduction oj Nitrates. Nitrates (N03“) 
are reduced to nitrites (N02“) by radiation. The 
nitrite can be detected by the formation of azo 
dies. 
9.03 Scintillation Counters 
Crystals such as Napthalene (Ci0H8), anthra- 
cene (C6H4:(CH)2:C6H4), calcium tungstate 
CaWOJ, silver chloride (AgCl), thallium-activated 
sodium iodide (Nal), thallium-activated potas- 
sium iodide (KI), and others have been found to 
have a relatively high fluorescent yield. These 
crystals, in conjunction with light sensitive devices 
such as high-gain photomultiplier tubes are in use 
as research tools, but as yet no successful survey 
instruments have been delivered; however, de- 
velopment of such equipment is in advanced 
stages. It is felt that the scintillation type counter 
can be utilized to overcome many of the serious 
problems of high resistance, insulation, and thin 
windows associated with alpha counting by ioni- 
zation chambers and proportional counters. In 
addition, it is felt that scintillation counters may 
provide a wide range instrument to replace the 
use of Geiger-Mueller counters for low intensity 
gamma detection and ionization chambers for high 
dose rate gamma survey. 
Some problems are encountered with the 
scintillation counter. There is a spectral sensi- 
tivity problem such as that discussed in conjunc- 
Decomposition oj Carbon Tetrachloride. 
Carbon tetrachloride (CC14) in the presence of 
water and oxygen decomposes under radiation 
into chlorine (Cl2), carbonyl chloride (COCl2), 
and hydrochloric acid (HC1). The chlorine can 
be detected by the starch iodide reaction or by 
more sensitive and stable indicators such as thio- 
Michler’s ketone. Other chlorinated compounds 
such as DDT, chloro- and hexachloroethane react 
in a manner similar to carbon tetrachloride. 
Reduction oj Mercuric to Mercurous Salts. 
Mercuric chloride (HgCl2) or iodide (Hgl2) is re- 
duced to mercurous (HgCl or Hgl) and probably 
to metallic mercury by radiation. An early 
equilibrium is reached between the reduction 
products and the original salts, however, the re- 
action can be made to go forward by having 
present an acceptor of oxygen. Such an acceptor 
is tetramethyl diamino diphenylmethane which is 
oxidized to a deep blue diphenylmethane dye. A 
mixture of mercuric (Hg++) chloride and thio- 
compound therefore undergoes a change from 
colorless to blue upon irradiation. There is a 
possibility that the mercurous salt (Hg+) or the 
fine mercury formed in this reaction can be utilized 
to catalyze some chemical reaction which would 
result in greater sensitivity. 
Reduction oj Cupric to Cuprous Salts. 
Cupric chloride (CuCl2) or bromide (CuBr2) is 
reduced to the corresponding cuprous salts 
(Cu2Cl2 or Cu2Br2) on irradiation. It has been 
32 RADIAC 
Figure 31. Schematic diagram of a scintillation counter. 
Radiation striking the phosphor releases light which is picked up in the electron multiplier tube and is subsequently 
transformed into a meter reading or earphone indication. 
tion with ionization chambers. Satisfactory pho- 
toelectric tubes require in the neighborhood of 100 
volts per stage and with 10 or more stages this 
presents the same high voltage problem discussed 
in conjunction with Geiger-Mueller counters. 
Since the photomultiplier tubes are light-sensitive, 
the tube and crystal must be encased in a light- 
tight coating. 
9.04 Other Possibilities 
Several other processes have been examined for 
their possible use as dosage-indicating devices. 
Electrets show some promise, but further investi- 
gation is necessary before their actual application 
to dosimetry may be used as a basis for long-range 
planning. 
33 Chapter 10 
PHOTOGRAPHIC DOSIMETRY 
10.01 The Film Badge 
Photographic films are in universal use for the 
measurement of gamma ray dosage. As a personal 
badge, they are especially valuable since they 
produce a permanent record which in many cases 
can be used for medical-legal purposes. As in the 
case of light, gamma rays produce developable 
images. Photographic materials find many labo- 
ratory uses for the measurement of radiation, and 
as such may find their way into the field laboratory 
(6). For the present, however, we will consider 
only dosimetric applications. 
A film badge as shown in figure 32 usually 
consists of a packet containing one or more photo- 
graphic fdms of dental size (l){ inches by 1% inches) 
wrapped in a thin material which is opaque. The 
whole unit may be sealed in a waterproof paper or 
cloth envelope. The sensitive emulsion consists of 
a thin layer of a silver halide and gelatin spread on 
a cellulose film base. The interaction of radiation 
with the silver halide is understood to be some type 
©f ionization which produces a developable latent 
image. The developing process converts the 
latent image into a deposit of black silver metal. 
Some sections of the film packet may be covered 
by a thin (1 mm) lead shield* designed to exclude 
beta particles, so that an examination of the film 
blackening behind the lead or in the clear may 
give an indication of beta exposure. The lead 
shield also serves to enhance the darkening due to 
gamma rays because of a large number of electrons 
ejected from the lead. 
Placing an identification number on the outside 
of the film badge packet and transferring this 
number to the light sensitive film presents some- 
what of a problem. If this is done manually, the 
time involved, except for minor numbers of badges, 
becomes prohibitive. Some investigations are 
being made into the possibility of using X-rays to 
expose a number punched out of a thin metallic 
sheet which would be incorporated into a section 
of the covering envelope. Today there is nothing 
which can be considered as a satisfactory identi- 
fication system for military usage. 
10.02 The Densitometer 
A densitometer is used to measure the blacken- 
ing of the film, and this is compared to the blacken- 
ing of standard calibrated samples. The sche- 
* Cadmium has had some use in film badge shields. 
Figure 32. Film badge. 
Top left is the badge with serial number on waterproof cover. Below are front and back views of packet with 
lead cross. Top center is an opened cover and lead cross; bottom, badge opened to show paper dividers and films. 
At right are two processed films. 
35 RADIAC 
In figure 36 the density is plotted against the log 
of relative exposure, and the characteristic curve 
of a film emulsion is obtained. 
10.03 Film Processing 
The characteristic curve will start with some 
minor density at A which the cellulose acetate 
backing contributes. Some exposure is required 
to overcome the inertia of the film in the toe por- 
tion A-B. The shoulder portion C-D shows that 
at some point continued exposure fails to make 
very much of a contribution to increasing the 
density. For the greatest accuracy only the linear 
portion of the curve B-C should be used, since 
the greatest change in density occurs with change 
in exposure. There is a limited range of sensitivity 
for any one emulsion; therefore, several emulsions 
may be combined into one film badge packet, to 
give an extended range (see sec. 15.08 on page 81). 
Variations in film processing can introduce 
possibilities of serious errors. The film density 
is a function of time and temperature of develop- 
ment, developer solution strength, and the degree 
of agitation in the developer. Every effort should 
be made to follow a standard processing procedure 
such as that recommended by the film manufac- 
turer. As a very rough rule of thumb, it can be 
stated that a one-degree change in developer 
temperature can introduce a three to six percent 
variation in the roentgen reading, and a sixty- 
second time variation may introduce five to 
ten percent variation. There are circumstances 
when these variations can be much greater. Film 
processing is therefore very critical and must be 
controlled carefully. Under the majority of field 
conditions it will be extremely difficult to maintain 
the required controls, and until automatic high 
speed developing and densitometric reading equip- 
Figure S3. Film badge carried in shirt pocket. 
matic arrangement of a densitometer is shown in 
figure 34 and a densitometer in use is shown in 
figure 35. 
The image of a small area of the film is allowed 
to fall upon a photocell which in turn is connected 
to a microammeter. Light falling directly upon 
the photocell will produce a reading, IG. When 
the film is put in the light path, some absorption 
will take place, and a lower reading, I, will result. 
The ratio y is called the opacity, O. The trans- 
parency, T, is the reciprocal of the opacity or J- 
-*■O 
The optical density, D, of the silver deposit on the 
photographic film is defined by the relation: 
D=log10 O=log10y 
Figure 84. Schematic arrangement of a densitometer used to determine film badge readings. 
36 RADIAC 
Figure 35. Densitometer in use. 
The density of each individual film badge must be obtained and compared against the density of similar 
films calibrated against known radiation sources in order to determine dosage readings. 
ment is put into use, the volume of film badges 
that can be processed is limited seriously. From 
the start of development to the completion of 
densitomctric measurement using standard tech- 
niques, a time of roughly one hour is required 
for one film. 
It is found that no two batches of the same film 
from the same manufacturer have exactly the 
same response to radiation. This can introduce 
serious difficulties if ignored and requires that a 
calibration be made for each batch. As in the 
case of other photographic materials film badges 
have a limited shelf life even under the best storage 
conditions. There are also gradual changes in 
the film characteristics with time which requires 
that continuous calibration checks be made. The 
method of calibration will be discussed in chap- 
ter 13. 
Although there are objections to film badges, 
they are a very important dosage recording device. 
37 RADIAC 
tection of any military participation in future 
atomic weapon tests. Radiation exposure lias 
become one of the standard entries in military 
health records (see fig. 37) and film badges, because 
of their permanence, are filed to substantiate any 
such entries. 
Figure 36. Characteristic curve of a film, badge emulsion. 
The size, weight, record permanence, simplicity, 
and cost when compared with the various dis- 
advantages, may outweigh the use of more 
complicated electronic devices which require 
considerable upkeep and adjustment. It is cer- 
tain that film badges will be used for health pro- 
Figure 37. Medical records. 
Radiation exposure has become a standard entry in 
military health records; and film badges, because of their 
permanence, are filed to substantiate any entries. 
38 Chapter 11 
CLOUD CHAMBERS AND ACCELERATORS 
The cloud chamber is one of the most useful tools 
for the scientific examination of the properties of 
the atomic nucleus and of the various particles and 
radiations. Such an instrument has no fore- 
seeable military applications; however, the cloud 
chamber is advertised widely, and a brief state- 
ment is considered essential to* give a well-rounded 
description of radiac instruments. 
Ions caused by a charged particle may act as a 
nucleus for condensation in a supersaturated 
vapor. Radiation passing through such a vapor 
will produce ions which will cause droplets of 
vapor to form that may be seen by the naked eye 
or photographed by a camera under certain condi- 
tions. When such cloud chambers are used in 
conjunction with magnetic fields, the curvature 
and extent of the vapor trails can be utilized to 
give indications of charge, velocity, mass, etc., of 
the initiating radiation. 
Another group of machines called accelerators 
are used as tools of the physicist in his examina- 
tion of the structure of matter. Descriptions of 
the linear accelerators, van de Graaf generator, 
cyclotron, synchrocyclotron, betatron, synchro- 
tron, Bevatron, etc., may be found in most 
modern physics texts (2) (7). They have no 
application to the problems of military radio- 
logical defense. It should be noted that a number 
of the radiac instruments herein described were 
developed for the health protection of personnel 
employed in the vicinity of high energy accelera- 
tors. 
39 Chapter 12 
SHAPE AND CHARACTERISTICS 
12.01 Introduction 
No attempt will be made in this article to dictate 
military characteristics for the various radiac 
instruments and equipments, but a slight indica- 
tion of the degree of evolution is considered of 
some value to personnel who are unfamiliar with 
the field. 
The portable instruments now available to the 
military are, in most instances, laboratory equip- 
ments which have been altered to hand carrying 
cases. They have undergone enough develop- 
ment so that they can render satisfactory military 
service as training instruments and, in the event 
of emergency, would no doubt give good service 
within the continental limits of the United States. 
It is doubtful, because of the peculiarity of 
construction and lack of standardization of 
certain components, such as high resistance 
resistors, Geiger tubes, electrometer tubes, and the 
like, whether these interim instruments would be 
entirely suitable in oversea military operations. 
Such instruments have not yet reached a point of 
service acceptability by either field or landing 
forces. It is anticipated that the development 
programs now under way will produce satis- 
factory equipment within the next 12 to 18 months. 
It is certain that if the necessity arose tomorrow, 
the interim instruments could be used to 
advantage. 
12.02 Physical Characteristics 
The great majority of the portable radiac 
instruments of the types in which we are interested 
are housed in rectangular metal cases of roughly 
250 to 500 cubic inches. Carrying has been by 
means of a handle on the top of the instrument 
and by a carrying strap attached to eyes on the 
ends of the instrument case. The instrument 
weights run between 7 and 15 pounds. 
Field tests during atomic weapon test explosions 
(8) have given us some criteria for the design of 
hand-carried instruments. There are virtually 
no indications as to proper form factor for instru- 
ments carried by pack, attached to the belt, etc. 
So far only one attempt has been made to deviate 
from the ordinary shoulder strap and handle 
type instrument. This deviation is the AN/PDR-8 
Geiger counter which is built to fit over the stom- 
ach, with the carrying strap running around the 
back of the neck. Several tests indicate that 
this method of carrying the instrument may have 
some slight advantage in going through hatches 
and up and down shipboard ladders. For any 
other type of use, it is found that the neck rapidly 
tires, making the neck strap less satisfactory 
than a strap which crosses the body over one 
shoulder. Also, the stomach-carried instrument 
does not lend itself to ease in being hand-carried. 
As in the case of everything else that one may 
be required to transport, the ultimate goal is 
zero weight and zero size; however, this not being 
practical, there are some immediate goals which 
may be set. It has been found that a rectangular 
shape, roughly eight inches long, five inches wide, 
and six inches high, weighing not over eight 
pounds, can be carried by hand or by shoulder 
strap for extended periods of time. In any opera- 
tion where instruments must be handed from 
person to person, such as from ship to small boat, 
or in and out of vehicles, etc., a rigid handle has 
been found more desirable than the hinged suit- 
case type. It should be obvious that a broad 
shoulder strap is desirable for comfort in instru- 
ment carrying, although some instruments come 
equipped with straps only slightly wider than a 
shoe string. 
One of the most important considerations is the 
location of the instrument’s center of gravity. 
Too many instruments have a tendency to fall 
on their sides when carried on the seat of a jeep 
or placed on the deck of a boat. Experiments 
indicate that the minimum angle from the vertical 
to which the instrument can be tilted prior to 
falling over is 35 degrees. 
Disposable transparent plastic covers have been 
used to prevent instrument contamination. In 
many cases these covers were more of a nuisance 
than they were worth. The majority of instru- 
871748°—50 4 
41 RADIAC 
ments now have smooth hard finishes from which 
contamination may be washed. Future designs 
should consider the elimination of any unneces- 
sary protuberances, such as meter housings, which 
would be contamination collectors. 
Many of the high range instruments will be 
used by personnel wearing gloves, and this fact 
has been overlooked in the placing of knobs and 
switches on a great number of instruments. 
There is also the possibility that some of the 
instruments will be used by personnel wearing 
gas masks and, therefore, meter markings should 
be such as to present no opportunity for mis- 
reading. Scale numbers which change with a 
change in the range scale, along with distinguishing 
colors, are certainly recommended. Also, a means 
for illuminating the scale for night operation is 
recommended. 
Military radiac equipments will, in ail prob - 
ability, have changeable scale markings with 
changes in scale ranges. In addition, the scales 
will have distinguishing colors. For gamma rate 
meters, the following range scale colors have been 
accepted: 
0—500 r/hr fire engine red 
0—50 r/hr light magenta 
0—5 r/hr orange 
0—500 mr/hr yellow 
0—50 mr/hr white 
0—5 mr/hr green-yellow 
0—0.5 mr/hr light blue 
It is anticipated that a color patch scheme 
will be standardized for dosage recording instru- 
ments, film badges, etc., which will match that 
of the rate meters somewhat as follows: 
500 r or higher fire engine red 
50 r—499 r light magenta 
5 r—49 r orange 
500 mr—4.9 r yellow 
50 mr—499 mr white 
An experienced field soldier, on examination 
of the better commercial Geiger-Mueller detectors, 
may be appalled at the bright chromium-plated 
Figure 38. Existing equipment tried during field problems is found to be lacking in many characteristics. 
42 RADIAC 
tube probe; or a marine may complain that it 
would be impossible to drag any of the ionization 
chamber instruments along when involved in 
jungle fighting. Others, depending on their 
missions, will find faults with any of the present 
equipments. This is the state of development. 
To date, the greatest emphasis has been placed on 
obtaining proper instrument response with the 
idea that once this has been achieved, some of the 
other characteristics will receive attention. 
12,03 Electrical Characteristics 
Characteristics will, of course, vary from 
instrument to instrument and will depend some- 
what upon the use for which the instrument is 
intended. Some of the more important character- 
istics which are somewhat unique to radiac 
instruments will be indicated. 
A. Ability to Zero in Field 
The electronic circuit should be so designed 
that it will zero automatically on high dose rate 
of the instrument under background radiation 
intensities less than 0.05 mr/hr. 
B. Metering Time Constant 
Depending on the purpose for which the 
instrument is used, after an initial warm-up 
period the time constant should be such that 95 
percent of the final reading is reached after a 
maximum period of one second. For low intensity 
ranges such as 5 mr/hr this time constant may 
be longer. 
C. Pressure and Temperature Effects 
The majority of commercial instruments 
having non-military standard batteries may be 
subject to many temperature problems. Most 
organic quenched Geiger tubes will cease to 
function a few degrees below zero Fahrenheit. 
Ion chamber instruments are subject to many 
difficulties with changes in pressure due to use or 
transport by air. Military gamma measuring 
chambers require constant reading over a change in 
elevation from sea level to 36,000 feet. Efforts are 
being directed toward covering the temperature 
range of —'40 to +125° F, 
D. Saturation Effects 
To prevent an erroneous assumption as to the 
absence of radiation, the instruments should show 
no effects of saturation of the detector component 
until radiation intensities of at least five times the 
maximum reading of the instrument are en- 
countered. 
12.04 Radiological Characteristics 
On page 12 an indication is given of the spectral 
sensitivity problem. It is felt that gamma 
response in roentgens should be held within ±20 
percent of air equivalent over the range 80 Kev 
to 5 Mev. At the same time, the instrumental 
inaccuracy should not be more than ±10 percent 
of the scale reading for any point above 10 percent 
of the scale for energies between 1 Mev and 
3 Mev. 
For beta survey purposes, wall thickness of 30 
mg/cm2 are recommended. Thinner windows of 
the order of 3-4 mg/cm2 will be required for beta 
admission during certain decontamination proc- 
esses. 
Instruments for alpha detection must record 
particles having a minimum range of 3 centimeters. 
43 Chapter 13 
CALIBRATION 
A problem which at first appears of little conse- 
quence is that of instrument calibration. Actually, 
this is an extremely serious problem to designers, 
manufacturers, and to users whether in laboratory 
or field work. There are two calibrations which 
must be considered: 
a. Spectral sensitivity, and 
b. Dosage rate. 
The first is a function of the materials, configura- 
tion, etc., of which the instrument is made. Mili- 
tary radiac equipment is checked for spectral 
response by the X-ray section of the National 
Bureau of Standards, and it is considered 
that they are not likely to change unless the 
instruments are damaged or altered. Unfortu- 
nately, the instrument evolution has not progressed 
to the point where one is willing to use them per 
se without continuous rate calibrations. 
If errors, some serious, are to be eliminated from 
quantitative dose rate measurements, then it is 
necessary to expose the instruments in substan- 
tially the same manner in which they are cali- 
brated. This does not mean that qualitative 
indications cannot be obtained when an instrument 
is not calibrated for a specific radiation. In the 
case of the portable Geiger-Mueller counter the 
instrument is calibrated for gamma radiation but 
is satisfactorily used to locate beta surface con- 
tamination. An extremely complex beta calibra- 
tion with rigid use restrictions would be required 
to make the Geiger-Mueller counting rate a 
quantitative measure of active material. 
Alpha calibrations are done with plutonium or 
uranium sources at the center of the plane of the 
external opening of the instrument. As a matter 
of interest, it can be stated that one gram of pure 
natural uranium emits a total of 2.5 x 104 alpha 
particles per second. Considerable effort must be 
placed in determining the absolute number of 
disintegrations for any sample to correct for self- 
absorption and geometry. 
Beta calibrations present a more serious prob- 
lem than do alpha, primarily because of scattering 
effects and absorption of the beta particles. A 
good number of standards are made by depositing 
on a foil a known amount of uranium oxide 
(U308). The foil having a density of 25 mg/cm2 
will absorb all alpha particles and only about five 
percent of the beta particles. Strontium 90 is 
also used as a beta calibration source. It should 
be noted that the methods of alpha and beta 
calibrations are not entirely satisfactory and that 
work is under way to develop better means of 
calibration. 
Radium encased in platinum and cobalt 60 are 
used as gamma radiation sources for calibration. 
Sources are calibrated at the National Bureau of 
Standards at periodic intervals. Information from 
the source calibrations allows a calculation of 
intensity at one centimeter from the source. 
Intensities at other distances are found by use 
of the inverse square law. 
In the case of radium, the following relation- 
ship exists: 
T _8.4m 
lRa~~dF 
where I is the dose rate in roentgens per hour at a 
distance d centimeters from a source of mass m 
milligrams. The half life* of radium being rel- 
atively long (1,600 years), there is little worry 
about changes in source weight over periods of 
months. Cobalt 60, on the other hand, has a half 
life of 5.3 years, and it is therefore necessary to 
include the elapsed time t in days from the date 
of source calibration. The radioactive cobalt is 
produced artifically in a rod of ordinary cobalt 
metal through neutron irradiation in an attunic 
pile. A number of atoms within the rod will not 
become radioactive; therefore, the weight of the 
sample is not necessarily indicative of the radio- 
activity. As a result, the source activity A in 
millicuries** giving a numerical quantity of dis- 
*The half life of a radioisotope is the time required to lose half of its activity. 
**Millicurie =1/1000 curie. The curie is generally accepted as that quan- 
tity of substance which decays at the rate of 3.7 x 10<® disintegrations per 
second. The millicurie (me) has a disintegration rate of 3.7 x 107 disinte- 
grations per second. 
45 RADI AC 
Three ionization chamber survey meters are calibrated against a cobalt 60 source. 
Figure 39. Gamma calibration. 
integrations per second at the time t must be given. 
The calibration relationships for Co60 are: 
ment and make adjustments in order to minimize 
personnel exposure. 
It should be noted that geometrical considera- 
tions limit the maximum intensity which can be 
obtained from a single source. This closest 
approach of the instrument to the source at which 
it can be considered that the square law still holds 
and at which the detector is receiving a uniform 
radiation may be taken as equal to 10 times the 
maximum dimension of the detector. 
The gamma calibration of film badges, dosi- 
meters, and other dosage reading is accomplished 
in a manner similar to that explained above for 
intensity meters except that the time of exposure 
at a given intensity must be measured carefully. 
0.693X1 
r 8.4A-e 5-3X365 8.4A-e-3-58X1°-4< 
/ _ 60 = — — 
lco d2 d2 
An open area usually is marked off into con- 
centric circles with the source of radiation placed 
at the center as shown in figure 39. Such an 
arrangement can be used for the rapid calibration 
of large numbers of medium level dose rate 
instruments. Instruments calibrated at extremely 
high levels, such as 100 to 500 roentgens per hour, 
require remote control devices to move the instru- 
46 Chapter 14 
OPERATIONAL INSTRUMENTATION 
14.01 Available Instruments 
The various instruments and techniques for 
radiation measurement have been covered in a 
rather complete but general way. As far as opera- 
tions are concerned, with the exception of the field 
laboratory, the following are the instrument types 
which are available for military use: 
1. Geiger-Mueller counters— 
Low level beta-gamma detectors for— 
a. Field detection. 
b. Warning. 
c. Decontamination detection. 
2. Ionization chambers— 
High dose rate gamma survey— 
a. Ground. 
b. Ground from the air. 
Direct and indirect reading personnel dosage 
recorders. 
Group dosage recorder. 
Alpha detectors in low beta-gamma back- 
ground. 
3. Proportional counters— 
Alpha detection and survey in medium beta- 
gamma background. 
Decontamination detection. 
4. Photographic film badges— 
Gamma dosage recorder. 
Indicator of beta exposure. 
Track plates for laboratory alpha measure- 
ments. 
A tabulation of use, state of development, etc., 
for various instruments is given in table III. 
In radiological warfare, whether it be atomic 
bombs or a radioactive agent, the chief radiations 
are the alpha and beta particles and the gamma 
rays. In the case of a high altitude bomb blast 
virtually all radioactivity is contained in the 
resulting cloud. Some of this material may fall 
out on the earth’s surface many miles from the 
blast, but in general the radioactivity of the fall-out 
will be low intensity alpha, beta, and gamma. As 
the explosion occurs closer to the ground, neutrons 
produced during fission may induce beta and 
gamma activity into the ground materials which 
absorb them. Also, as the explosion occurs closer 
to the ground, there will be certain quantities of 
unused fissionable alpha producers and beta- 
gamma emitting fission products which will be 
deposited on the ground. Alpha, beta, and 
gamma emitters are possible radiological agents, 
although they will more probably be either beta or 
gamma or a combination of beta and gamma (see 
page 3). 
In the case of an under-water bomb explosion, 
beta-gamma active fission products and unfis- 
sioned alpha-emitting bomb materials will be held, 
to a large degree, in a cloud which spreads out and 
rains down on the surrounding landscape. Cer- 
tain beta-gamma activity will be produced through 
the neutron irradiation of water contaminants such 
as the salt in sea water. The contaminated cloud 
may contain radiating materials which will give 
lethal doses with exposures of a fraction of a 
minute. This cloud material in settling onto the 
surface of the earth may deposit contamination 
which will produce gamma dosage rates of several 
hundred roentgens per hour. 
Atomic bomb explosions in contact with the 
ground or underground will result in contamina- 
tion somewhat different from that occurring with 
the one under-water shot which has been fired. 
Beta-gamma active fission products and unfis- 
sioned alpha emitting bomb materials may be 
held in a large cloud of dust and earth particles 
which may spread out and settle on the surround- 
ing landscape. In the immediate vicinity of the 
point of detonation will be a crater depending in 
size on many different variables such as density 
and type of soil, strength of bomb, depth of ex- 
plosion, etc. The crater, in addition to the high 
activity resulting from the various bomb con- 
taminants, will have neutron-induced activity and 
shortly after the blast may have gamma dosage 
rates of many hundreds of roentgens per hour. 
47 RADI AC 
Table III.—Use of various radiac instruments 
Instrument 
Purpose 
Radiation 
Use 
Remarks 
Alpha 
Beta 
Gamma 
Pocket dosimeter 
Individual ex- 
X 
Field or laboratory 
High cost compared to pocket 
chamber. Requires sepa- 
rate charger. 
Drift meter. 
posure 
Rate of ex- 
X 
X 
X 
Secondary standard in 
conjunction with labo- 
ratory. 
Pocket chamber 
posure 
Individual ex- 
X 
Requires a separate charger- 
reader. 
Many problems involved with 
thin windows. 
Use for high dose rate radi- 
ation measurement. 
Many problems involved with 
thin windows. 
Limited to detection and low 
dose rate. 
Thin window cham- 
ber 
Chamber survey 
posure 
Rate of ex- 
posure 
Rate of ex- 
X 
X 
X 
X 
In conjunction with lab- 
oratory. 
Proportional counter 
posure 
Disintegration 
rate 
Rate of ex- 
X 
In conjunction with lab- 
oratory. 
Field or laboratory 
Geiger counter 
X 
X 
Scaling circuit 
posure 
Cumulative 
X 
X 
X 
Laboratory 
Count rate meter 
record 
Rate of ex- 
X 
X 
X 
Laboratory. 
Scintillation counter. 
posure 
Rate of ex- 
X 
X 
X 
Film badge. _ _ 
posure 
Individual ex- 
X 
X 
Field or laboratory 
Teriffic problems involved with 
development in any quan- 
tity. Gives a permanent 
record. 
Track plates _ _ 
posure 
Degree of con- 
tamination 
Individual ex- 
X 
Laboratory 
Color crystals and 
liquids, chemicals, 
photo conductive 
crystals, etc. 
Electrets 
X 
posure 
Individual ex- 
X 
x 
x 
posure 
One of the reasons for the high beta-gamma 
activity immediately following an atomic bomb 
explosion is the short half-life elements either 
produced as fission products or as the result of 
neutron irradiation. This high activity results in 
the rapid decay and rapid removal of the beta- 
gamma hazard. In the case of an air burst, 
depending on height and many other variables, 
the area beneath the blast may be safe from an 
emergency military beta-gamma standpoint, with- 
in less than an hour after the burst. This is not 
the case if alpha emitters remain after a bomb 
explosion. These will not show high initial 
activity and will not decay immediately to a point 
of no concern but may remain for years to plague 
occupants of a contaminated area. Being alpha 
and not active in enormous quantities, they may 
be overlooked because of the difficulty of detec- 
tion, and perhaps through their introduction into 
foods, water, ventilating systems, etc., may pre- 
sent a definite hazard to a long term military 
organization. 
To give indications of possible military usage, 
instruments will be discussed in conjunction with 
each type of radiation. 
14.02 The Alpha Particle 
Because of the very short range and penetrating 
power, alpha particles are very difficult to meas- 
ure. A 5 Mev alpha particle has a range of only 
3.5 centimeters in air; therefore, the maximum 
distance a detector with an air window can be 
48 RADIAC 
Figure 40. Checking meat for alpha contamination with a poppy-type portable proportional counter. 
from such a particle is 3.5 centimeters. A closer 
distance is required, since not all particles will 
travel at right angles to the emitting surface. 
Partial shielding by the emitting surface will also 
reduce the travel distance as will lower particle 
energies. 
Detailed alpha measurements will be made in 
conjunction wuth decontamination work and will 
be specified in alpha disintegrations per unit of 
time per unit of surface area. 
It is difficult to establish general rules for all 
types of alpha emitters. Their hazard is internal 
from inhalation and ingestion, and different ele- 
ments are deposited in different organs and as a 
result will produce varying degrees of damage (9). 
As a crude attempt to establish over-all working 
values for field use, the following are given; 
(a) food not to exceed one meal—a maximum level 
of 300 disintegrations per minute per square 
centimeter of surface; (b) air containing uniform 
dust contamination measured at any surface to 
have a level of not more than three disintegra- 
tions per minute per square centimeter for a maxi- 
mum exposure of eight hours; and (c) drinking 
water, when activity is measured on an open sur- 
face, not to exceed 1,000 disintegrations per 
minute per square centimeter for no more than a 
one-day supply. It must be remembered that 
the effects of alpha activity, whether from food, 
drink, or breathing, are cumulative. 
An ionization chamber such as Radiac Set 
AN/PDR-20 will measure the total ionization 
produced in the chamber and not the number of 
disintegrations. However, a rough calibration in 
terms of number of disintegrations can be made 
so that the instrument is not completely useless. 
It must be remembered that beta and gamma 
activity will contribute to the reading, although 
their contribution can be estimated by the use of 
an alpha absorbing shield in front of the window. 
Portable proportional counters (fig. 40) such 
as Radiac Set AN/PDR-10 with a large probe 
window will be the primary alpha detectors. 
These instruments will be adjusted to respond only 
to highly ionizing events and will be useful except 
in cases where the beta-gamma to alpha ratio 
exceeds 107. The instrument is capable of high 
counting rates. Operation is limited to relatively 
dry weather, since high voltage leakage in the 
chamber will result in spurious counts. 
49 RADI AC 
Neither Geiger-Mueller counters nor film badges 
will be used for alpha detection in military opera- 
tions. 
Alpha counting must be performed by well- 
trained monitors working in conjunction writh the 
field laboratories in which a large portion of the 
determination of alpha hazard will be made. For 
example, none of the instruments we have just 
discussed are satisfactory for measuring alpha 
activity in drinking water or in air. A photo- 
graphic process involving nuclear track plates may 
be used in some laboratory alpha investigations (6). 
14.03 The Beta Particle 
Faulty measurement of beta particles probably 
presents the greatest hazard of any radiations to 
be encountered in military operations. Very low 
energy (soft) beta particles present virtually the 
same measuring problems as do alpha particles. 
As a result, the soft beta particles, winch are 
dangerous if inhaled or ingested, may be ignored. 
High energy (hard) beta particles, on the other 
hand, may penetrate gamma shields and give 
what appears to be enormously high gamma 
readings. 
Beta measurements may be made both in con- 
junction with decontamination and area survey. 
Beta particles and gamma rays will always be 
found in some ratio. For example, immediately 
following a bomb blast the ratio will be much 
higher than, say, one month later. Beta particles, 
because of their low penetrating power, are as a 
general rule considered as only an ingestion or 
inhalation hazard. As in the case of alpha 
emitters, the various elements will lodge in different 
internal organs; therefore, the beta tolerance 
levels are primarily a function of the emitting 
element. Detailed determination of the specific 
elements and beta-gamma ratios will be a function 
of the field laboratory. In many cases, field 
laboratory information will allow7 a monitor to 
determine beta hazard through gamma measure- 
ments. 
Specific information is lacking on the tolerance 
range which will be referred to in military opera- 
tions. Ionization chamber instruments such as 
the AN/PDR-20 with thin windows and the 
AN/PDR-8 (series), 27, and T-2 Geiger counters 
can be used to indicate beta particles. Both the 
ionization chamber and the Geiger-Mueller counter 
(fig. 41) will read the combined beta plus gamma 
activity. However, it is possible to estimate the 
gamma contribution by placing a beta absorbing 
shield over the chamber or tube window. In the 
case of the Geiger-Mueller counters AN/PDR- 
T-2 and AN/PDR-7, having thin wall tube sec- 
tions around 30 mg/cm2, beta particles of energy 
less than 160 Kev will be excluded. The very 
thin 3-4 mg/cm2 windows associated with Radiac 
Sets AN/PDR-8 (series), and AN /PDR-27 will cut 
out soft beta activity below 50 Kev. 
Beta measurements with thin wall Geiger- 
Mueller tubes in instruments calibrated in roent- 
gens (the roentgen will be discussed under gamma 
ray measurements) may cause some trouble, since 
there is no relationship between the roentgen (a 
measure of electromagnetic radiation) and quan- 
tities of beta particles. With the probe shield 
open and the tube directly exposed to beta radia- 
tion, the instrument will in general read several 
times the gamma ray reading with the shield 
closed. (See discussion on page 55.) This fea- 
ture adds to the sensitivity of the equipment when 
used as a detector for decontamination. It must 
be emphasized that the beta particle reading bears 
no relation to the roentgen and cannot be con- 
verted into these units. Only for beta particles 
of one specific energy can a certain roentgen rate 
reading be stated as equivalent to a certain num- 
ber of disintegrations per second. This will not 
be true for beta particles of other energies. This 
entire problem has led to the recommendation 
that beta-gamma sensitive Geiger counters have 
an inscription on the dial: mr/hr—hard gamma 
only. 
Proportional counters find little use in beta 
measurements, particularly since any counter 
sensitive to hard beta will be sensitive to gamma 
rays, and the selective advantage of the propor- 
tional counter is lost. 
As previously indicated, personnel film badges 
utilize a lead shield over a portion of the film so 
that the unshielded section of the badge may give 
a beta plus gamma reading and the shielded por- 
tion a gamma reading only. The beta exposure 
determined by this method cannot be considered 
too satisfactory since the waterproof envelope and 
light-tight paper container, plus the cloth and other 
substances in the wearer’s pocket, will give an 
unknown degree of beta shielding. If photo- 
graphic film badges are to be used to any extent 
for the measurement of external beta exposure 
50 RADI AC 
Figure 41- Geiger counter in use with beta shield open to increase detection sensitivity in checking for ground contamination 
during military operations, it will be necessary to 
prescribe exact methods of attaching the badge 
to the person. This in itself is not a complete 
solution, since body shielding, equipment, etc. 
may give degrees of shielding which will give 
false results. 
14.04 The Gamma Ray 
Because of its range and great penetrating 
ability, the gamma ray presents the least difficulty 
of measurement. As stated previously, it is fortu- 
nate that the greatest military preoccupation will 
be with gamma rays. This of course, means that 
the greatest emphasis must be placed on accurate 
gamma-measuring instruments. 
The unit of photon absorption, called the 
roentgen, is universally used for measurement of 
gamma ray dosage. In terms of this unit we state 
that the permissible amount of gamma radiation 
to which the body may be exposed for routine, 
every-day peace time operations is 0.1 roentgen (r) 
or 100 milliroentgen (mr) per day. This is in the 
process of being revised downward to a total of 300 
mr per week. For the purpose of performing some 
especially important mission in conjunction with 
field tests of atomic weapons, a maximum single 
51 RADIAC 
exposure of 3 r is prescribed, provided no further 
exposure is allowed over a period of 30 days. In 
the event of atomic attack, exposures up to 75 r 
(perhaps 100 r) will be permitted as one of the 
normal hazards of war. Exposures of 75 r or 
greater are of considerable interest to commanders 
for the further employment of personnel and to 
medical officers for proper treatment of casualties. 
In 1928 an international committee for radio- 
logical units defined the roentgen as the quantity 
of x or gamma radiation such that the associated 
corpuscular emission over 0.001293 gram of air 
produces, in air, ions carrying one electrostatic unit 
of quantity of electricity of either sign. It turns 
out that one cubic centimeter of dry air under 
standard conditions of temperature and pressure 
weighs 0.001293 gram, and that 2.083xl09 ions of 
either sign are required to produce one electrostatic 
unit. Further examination reveals that the aver- 
age energy of 32.5 electron volts required to pro- 
duce one ion pair can be converted into 5.24 X 1013 
electron volts per gram of air or 83.8 ergs per gram 
of air. It should be noted that this definition 
makes the roentgen a unit of dose rate (absorption) 
rather than a unit of intensity. 
An ionization chamber such as the AN/PDR-20 
which has discriminating slides for the purpose of 
additional alpha and beta measurements is useful 
as a survey instrument when the humidity is not 
at a point which destroys chamber insulation. 
Chambers with provisions for thin windows are 
not constructed to withstand rough usage. This 
instrument must be used by well-trained monitors 
having a close liaison with a field laboratory. Its 
primary usage would be in conjunction with de- 
contamination activities. 
Completely sealed ionization chambers such as 
the radiac meter IM-3/PD and the AN/PDR-T-1 
will be standard equipment for reconnaissance and 
scouting parties and for damage control equipment 
on board ship (fig. 42). These instruments, which 
in some cases will be designed to read gamma dose 
rates which would produce lethal dosages in less 
than one hour (500 r/hr), will be used to monitor 
unusually hot areas in which urgent work must be 
accomplished. 
Ionization chambers such as the non-self-read- 
ing pocket chambers, DT-16/PD, DT-35/PD, etc., 
and the self-reading quartz fibre pocket dosimeters 
(electroscope), IM-9/PD, IM-50/PD, etc., will be 
used to record individual gamma ray dosage. 
Trained monitors most certainly will be equipped 
with either the pocket dosimeter or with a pocket 
chamber and chamber reader. In cases where a 
record of dosage is required, but where it is not 
considered advisable for the wearer to know that 
dosage, the pocket chamber will be used. 
Under some circumstances it is desirable to 
determine gamma intensities from a remote posi- 
tion. It is most probable that the detector ele- 
ment of any such instruments will utilize ioniza- 
tion chambers. Two possibilities present them- 
selves for projecting instruments into a contam- 
inated area: (a) rocket or gun fired missile, and (b) 
an air droppable unit. The latter is under devel- 
opment as the AN/USQ expendable unit with the 
AN/ARR-29 receiver. It has been found that 
the problems concerned with radiation sensitivity 
are minor in comparison to those of ruggedness and 
data telemetering. Development work is also 
under way to evolve airborne radiac equipment 
capable of interpreting ground gamma radiations 
from any altitude. 
Ionization chamber instruments have been 
designed to perform the function of closing relays 
upon reaching predetermined dose rates of gamma 
radiation. Instruments of this type will be of 
use in limited numbers for sounding alarms, clos- 
ing ventilators, etc., as in the case of the AN/ 
ADR-1 for planes flying into a radioactive cloud. 
Chamber instruments can be used to record the 
total accumulated dose in certain restricted areas 
such as specific shipboard compartments, the 
pilot compartment of an airplane, or the interior 
of a tank. The AN/ADR-2 airborne gamma do- 
simeter is yet to be evaluated, and the AN/PDR-2 
group dosimeter requires many improvements to 
make it satisfactory for use outside the laboratory. 
Film badges will continue to record gamma ex- 
posure of personnel involved with training (fig. 
43) participating in atomic weapon tests, and 
peacetime uses of atomic energy. Because of the 
many disadvantages associated with film badges, 
they may never be used in extensive military 
operations. Pocket chambers or pocket do- 
simeters will probably replace film badges, so that 
immediate spot readings of dosage can be made. 
If a permanent record is required for medical or 
legal reasons, it is relatively simple to make an 
automatically recording reader. 
Geiger-Mueller counters such as the AN/PDR- 
T-2, AN/PDR-8 (series), and AN/PDR-27 are 
52 RADIAC 
Figure J+2. Ionization chamber being used for gamma survey work by a shipboard damage 
control team. 
Figure 43. Individual dosimetry. 
Film badge and dosimeter are collected upon leaving contaminated area. 
53 RADI AC 
Figure 44- Helicopter ground monitor. 
The Geiger counter is used for an air check of ground gamma contamination. 
Figure 45. Decontamination. 
The portable Geiger-Mueller detector will be a primary instrument for use in equip- 
ment decontamination. 
54 RADIAC 
Figure 46. Checking hand contamination. 
The probe beta window is left open to increase sensitivity in checking clothing, hands, feet, etc. Earphones as 
well as meter indication are used in checking with the Geiger counter. 
convenient portable instruments for gamma ray 
detection (fig. 44). Note that the word detection 
is used rather than survey. The counter range 
of the equipment is limited to the region from 
background to intensities slightly in excess of 
those which will give daily peace-time tolerance 
dosages (0.1 r) during a normal working day. 
As such, these instruments will have a primary use 
in conjunction with decontamination work (fig. 
45). The probe makes them especially convenient 
for rapid examination of clothing, hands, feet, 
etc. (fig. 46). The Geiger-Mueller counter as the 
most sensitive gamma detector may have some 
usage as an early stage warning device for air- 
borne radioactive particles and radioactive gases. 
Because it counts ionizing events rather than the 
ionization produced in air, it is not possible to 
calibrate the Geiger-Mueller counter in terms of 
roentgens except for a definite energy spectrum. 
In many cases calibrations are made in milli- 
roentgens per hour for sources such as a standard 
radium sample. All other samples of radiations 
within the radium spectrum then can be compared 
in terms of milliroentgens per hour. Due to a 
very definite wave length dependence and the 
efficient counting of hard beta particles, it is 
unwise to use the Geiger-Mueller counter as a 
quantitative recorder. 
The proportional counter is not used as a 
gamma ray measuring instrument, since the 
primary use of the proportional counter is for 
discrimination against gamma rays (and beta 
particles) for the purpose of alpha particle meas- 
urement. 
14.05 The Field Laboratory 
As can well be seen from an examination of 
previous sections, the field laboratory is probably 
as important as any individual instrument. Its 
instrumentation, working around the principles 
we have discussed, must work in conjunction with 
chemical and other analytical methods to give 
rapid, accurate indications of hazards. It is 
readily apparent that with a minor amount of 
training and supervision a man can take care of 
himself and make satisfactory gamma surveys. 
In the case of alpha and beta particles, highly 
trained monitors are required. A great amount 
55 RADIAC 
of decontamination work in connection with alpha 
and beta emitters will be directly tied into findings 
by the laboratory. The present designs of radiac 
equipment used for the detection of alpha and 
beta radiations do not lend themselves to ruggedi- 
zation and these instruments may be used most 
properly in operations directly tied to a field 
laboratory. Some extremely important functions 
such as the examination of drinking water (fig. 47) 
can be handled only with very special laboratory 
techniques. 
Having located radioactive areas and evaluated 
the immediate hazard, the laboratory can be used 
to determine how long the areas will remain 
dangerous and what measures, such as covering 
with earth, etc., are required prior to occupation 
or use. The field laboratory can make contribu- 
tions regarding the composition, efficiency, etc., of 
enemy weapons. 
Only through use and experimentation will all 
the components of a field laboratory be established. 
No attempt will be made to visualize the various 
analytical chemical equipments which will be 
required, but a rough guess as to instrument types 
is given below: 
1. Scaler for beta and gamma counting. Scale 
of 1,000, mechanical register, and timing mech- 
anism. 
a. Variable regulated power supply from 
approximately 100 to 2,500 volts. 
b. Geiger-Mucller and proportional counter 
probes. 
c. Special ion chambers. 
2. Counting rate meter for beta and gamma 
sampling. 
a. Variable regulated power supply from 
approximately 100 to 2,500 volts. 
b. Geiger-Mueller and proportional counter 
probes. 
c. Variable speed strip recorder. 
3. Gas flow proportional counter for alpha sam- 
pling, IM-ll/UD, with scaler and register. 
4. Miscellaneous accessories such as lead shields, 
thin window tubes, equipment for sample prepa- 
ration and determination of weight, sample hold- 
ers, etc. 
5. Filter type dust collector and electrostatic 
type dust collector. 
6. Photographic equipment for alpha track 
measurements. (Nuclear track plates.) 
a. Microscope. 
7. Instrument calibration standards. 
a. Secondary standard instrument such as 
the radiac meter IM-7/PD quartz fibre 
survey meter. 
b. Calibration sources. 
The field laboratory will be a most important hazard-evaluating unit during atomic warfare. 
Figure \7. Laboratory. 
56 RADIAC 
8. Special survey instruments such as: 
a. AN/PDR-20 thin window chamber. 
b. AN/PDR-10 alpha proportional counter. 
14.06 Other Establishments 
It is anticipated that the various services will 
establish a number of organizations within the 
zone of the interior, and at perhaps some advance 
bases, in which practically all the radiac instru- 
ments mentioned herein will be used along with 
laboratory equipment with such sensitivities and 
delicateness as to be completely ruled out of the 
field laboratory category. This equipment will 
be used to give thorough scientific checks on the 
results of the field laboratories. 
One very important device which will be used 
at any major decontamination center or at any 
base doing extensive work on contaminated equip- 
ment is the so-called hand and foot counter such 
as the AN/UDR-10 which is used to monitor 
personnel leaving working areas. 
871748°—50 5 
57 Chapter 15 
DESCRIPTION OF ACTUAL INSTRUMENTS 
15.01 The Field in General 
and numbers with the types of instruments we 
have been discussing. 
The writer may not be familiar with all instru- 
ments which have been produced and are being 
produced; therefore, inclusion or omission of a 
specific manufacturer’s equipment is not necessar- 
ily to be construed as either condemnation or praise. 
Indications will be made as to whether an instru- 
ment is obsolete, etc. The following code will be 
used: “o”—obsolete; “i”—in present military 
use; —anticipated for future military use. A 
tabulation of instruments of interest is given in 
Appendix I. 
The great majority of the instruments described 
herein are unclassified. Usually there will be no 
classification on any instruments issued for gen- 
eral use. 
It is desired to give a detailed description of the 
physical properties of commercial and military 
instruments which are making their way through- 
out the Defense Establishment. In addition, 
some instruments which are perhaps obsolete or of 
no military value have been so widely discussed 
that they will be included to show their relation 
to other such equipments. Laboratory instru- 
ments are not discussed and personnel interested 
in these equipments are invited to examine Refer- 
ence (10). For security reasons, a good number of 
instruments which were developed under the 
Manhattan District had code names. Also, some 
commercial model numbers have come into use. 
An effort is made here to correlate these names 
15.02 Dosimeters and Pocket Chambers 
Pocket dosimeters 
Pocket chambers 
Radiation detected __ _ _ 
Gamma _ 
Gamma. 
100 mr, 200 mr, 100 r, 
Ionization chamber. 
5 cc (less with high range). 
Separate reader. 
1 oz. 
Size of fountain pen. 
in. diameter 4)4—5)4 in. long. 
Full scale ranges 
100 mr, 200 mr, 10 r, 50 r, 100 r 
Detector 
Ionization chamber 
Volume of chamber __ 
2.5 cc 
Indicator. ... 
Image of electroscope fiber on calibrated 
reticle of microscope. 
1 oz 
Weight _ _ 
Shape._ 
Size of fountain pen 
Dimensions. _ 
)4 in. diameter, 4—4% in. long 
A. Pocket Dosimeters 
Manufacturer 
JAN Number 
Mfg. model Number 
AEG Number 
Full scale reading* 
Distinguishing 
color 
A. 0. Beckman Company (/) _ 
IM-50/PD_ 
PIC-10A 
200 mr _ _ 
Silver, 
200 mr_ 
Black. 
Cambridge Instrument Com- 
IM-51/PD 
BM 17400 
PIC-9 A 
200 mr 
Grey. 
pany (i). 
Kelley-Koett Manufactur- 
IM-9/PD (Set AN/ 
K-100_ 
PIC-7 A 
200 mr 
Black. 
ing Company (i). 
PDR-3). 
K-109_ 
PIC-7A1 
200 mr. _ _ 
Black. 
K-110 
PIC-7A2 
200 mr. _ _ 
Black. 
IM-9A/PD 
K-lll 
PIC-7A3. . 
200 mr 
Black. 
IM-19/PD 
K-150 (o), 151 (t) _ 
PIC-7B 
10 r 
Blue. 
IM-20/PD __ 
K—160 (o), 161 (t)-_ 
PIC-7C 
50 r 
Red. 
K-170 [o), 171 
PIC-7D 
100 r. 
Purple. 
Landsverk (o) 
IM-9( )/PD (Set 
L-200 
PIC-7 A 
200 mr. 
Silver. 
AN/PDR-3( )). 
*A number of 100 mr dosimeters bave been manufactured for use within Atomic Energy Commission laboratories. 
871748°—50 6 
59 RADI AC 
Shown from left to right are: Cambridge 200 mr; Kelley-Koett Models, K-110 (200 mr), K-151 (10 r), K-161 
(50 r), K-171 (100 r); Kelley-Koett charger; Beckman 200 mr and Beckman charger. 
Figure J+8. Dosimeters and chargers. 
Manufacturer 
JAN No. 
Mfg. model 
number 
AEC No 
A. 0. Beckman Co. (/) 
AY-9A 
Cambridge Instrument Company (i) 
Chatham Electronics (i) 
PP-527/PD 
PP-354/PD 
BM- 18230. 
P-800 . 
AY-7 A 
Kelley-Koett Mfg. Co. (t) 
PP-354A/PD 
PP-311A/PD (Set AN/PDR-3) 
K-135 
AV-2D 
Landsverk (o) _ _ 
PP-354B/PD. 
PP-311/PD (Set AN/PDR-3) 
L-300 
AV-2B 
B. Pocket Dosimeter Chargers 
60 RADIAC 
Figure 49- Electrostatic dosimeter charger PP-S54A/PD. 
This small unit, is approximately 2% inches wide, l}i inches high, and inches deep (including protuber- 
ances). Charging is accomplished by placing the dosimeter in the hole to the left, then turning the friction knob 
shown on the right. See figure 6. 
C. Pocket Chambers 
Manufacturer 
JAN No. 
Mfg. model number 
AEC No. 
Full scale 
sensitivity* 
Color 
Kelley-Koett Mfg. Co. (i) _ 
DT-35( )/PD (Set AN/ 
K-700 
PIC-2E 
200 mr 
Black. 
PDR-21). 
Nuclear Instrument and 
DT-16A/PD (Set AN/ 
3340 
PIC-1B __ 
200 mr _ _ 
Grey. 
Chemical Co. (i). 
PDR-4). 
Victoreen Instrument Co. 
DT-16/PD (Set AN/ 
352 
PIC-2C-- .. 
200 mr _ _ 
Black. 
(»)• 
PDR-4). 
Victoreen Instrument Co. 
353 
100 r 
(Black with 
ifi) 
(magnetic 
magenta 
charging 
color patch). 
device). 
*A number of ICO mr pocket chambers have been manufactured for use within the Atomic Energy Commission laboratories. 
61 RADIAC 
Figure 50. Pocket chambers and charger-reader. 
Victoreen model 353 100 r (left) and model 352 (DT- 
16/PD) 200 mr pocket gamma chamber are shown with 
the Kelley-Koett model K-425 (PP-43 ( ) /PD) 200 mr 
charger-reader. Chambers by other manufacturers are of 
comparable size and shape. 
D. Pocket Chamber Charger-Reader 
Tungsten fibre electrostatic voltmeter is 
used for charging and reading the residual charge 
on pocket chambers. Indication of reading comes 
from a projected image of the electroscope fibre 
on a calibrated reticule in a viewing microscope. 
Figure 51. Victoreen Minometer type charger-reader. 
The chamber is placed in the horizontal tube at the right 
of the picture. Readings are made through the vertical 
tube. Charging is accomplished by means of the button 
on the side of the instrument. 
Manufacturer 
JAN No. 
Mfg. model 
number 
AEG No. 
Full scale 
reading 
Kelley-Koett Mfg. Co. (i) (quartz 
fibre). 
(2 lb., 11 oz. battery operated) 
Victoreen Instrument Co. Minometer 
PP-43( )/PD (Set AN/PDR-21) _ _ 
PP~316/PD (Set AN/PDR-4) 
K-425 
287 
AE-1B 
AE-2A 
200 mr. 
200 mr. 
(i) (tungsten fibre). 
(6 lb., 110 v. A. C. operation) 
Victoreen High range Minometer (/) 
(tungsten fibre). 
(Weight, 6 lb., dimensions, 5in. 
wide x 7 in. long x 5 in. high exclu- 
sive of sight tube: 8 in. high over 
all. For battery operation. Mag- 
netic charging device.) 
392 
100 r. 
62 RADIAC 
Direct meter reading electrostatic voltmeters 
are used for charging and reading 200 mr pocket 
chambers. 
15.03 Quartz Fibre Survey Meter 
The original instrument of this type (IM-7/PD) 
is the Lauritsen Electroscope manufactured com- 
mercially by the Fred C. Henson Company. As 
such, this is an exceedingly accurate instrument 
for laboratory work, but it is not well adapted to 
field usage. 
A modified Lauritsen electroscope is manufac- 
tured by the Kelley-Koett Manufacturing Corn- 
Manufacturer 
Mfg. model 
number 
AEC No. 
Nuclear Instrument and Chemical 
Co. (i) 
2050 
AE-5A 
(10 in. long x 6 in. wide x 5}£ 
in. high; weight, 8 lbs. For 
110. v. A. C. operation. Can 
be used to enlarge 200 mr 
pocket dosimeters.) 
Figure 53. Radiac Meter IM-7A/PD quartz fibre drift 
alpha, beta, and gamma survey meter. 
The beta window is on the far end of the instrument 
with the alpha window on the bottom. Readings are 
made through the vertical tube. 
Figure 52. Nuclear Instrument and Chemical Company 
model 2050 charger-reader 
A direct reading of chamber charge is given on the 
meter. 
63 RADI AC 
pany (previously by the Laudsverk Electrometer 
Co.) having the following characteristics: 
JAN No. (/) IM-7A/PD. 
Mfg. model No K-320. 
AEG No SIC-5A. 
Radiation detected__ Alpha, beta, gamma. 
Scale ranges 0-100 mr/hr. 
(gamma). 0-1000 mr/hr. 
Detector Ionization chamber—25 in.3 
Indicator Rate of drift of electroscope fibre 
over a calibrated reticle scale in 
viewing microscope. Approxi- 
mately 6-8 seconds required to 
read true indication. An auto- 
matic flashing light timer is em- 
ployed. 
Weight 3}i lbs. 
Dimensions Main case; 6}i in. long, 4 in. wide, 
6 in. high. Microscope tube ex- 
tends 23/i in. above case. 
Window screens Beta—0.001 inch cellulose acetate. 
Alpha—0.0002 inch nylon. 
1 5.04 Ionization Chamber Survey Meter 
Figure 54- AN/PDR-T-1 gamma survey ionization 
chamber. 
Controls are shown for zero set and range. A push- 
button for meter illumination is at the forward end of the 
carrying handle. 
A. Gamma Ionization Chamber Survey Meter 
Manufacture 
Model number: 
Kelly-Koett Mfg. Co. (i)__ 
National Technical Labs. 
CO. 
Victoreen Instrument Co. 
(0. 
Manufacturers’ 
K-350 
MX-6 
247A*. 
JAN 
AN/PDR-T-1 
IM-40/PD 
IM-3/PD. 
AEG 
SIC-18A 
SIC-15A 
SIC-9B. 
Scale ranges (mr/hr) 
0-5, 0-50, 0-500, 0-5000, 
0-50,000. 
0-5, 0-50, 0-500, 0-5000 
0-2.5*, 0-25, 0-250, 0-2500. 
Detector 
Ionization chamber 
Ionization chamber 
Ionization chamber. 
Volume (cubic inches) 
54 
30.5 
56. 
Wall 
Acjuadag-coated polysty- 
rene. 
Aquadag-coated steel 
3/W polyethlene. 
Filling 
Air 
Monochloro-difluoro meth- 
ane. 
Air. 
Pressure 
Atmospheric 
3 lb. gage _ 
Atmospheric. 
Indication 
Meter 
Meter _ 
Meter. 
Useful operating life (hours) _ _ 
600** 
200 
30. 
Weight (pounds) 
10 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
cc\ 
12 Ys. 
Shape 
Rectangular 
Rectangular 
Rectangular with vertical 
cylindrical ends. 
Dimensions (length x width x 
height). 
10 x 6 x 7)4 including 
handle. 
9 Yz x 5 x 6 
10 % x 5% x 126%4. 
Case _ Welded steel with baked 
olive drab enamel. 
*The Model 247B has scale ranges of 0-25, 0-250, 0-2500, and 0-25,000 mr/hr. 
**Exclusive of battery for meter-illuminating light. 
Welded aluminum grey 
hammertone finish. 
y» in. cast aluminum. Baked 
grey enamel. 
64 RADI AC 
The AN/PDR-T-1 is the first ionization 
chamber gamma survey meter to be built to 
military specifications. These specifications were 
evolved from the Sandstone operational tests of 
commercial instruments (8) such as the 247A 
(IM-3/PD) and the MX-6 (IM-40/PD). The 
AN/PDR-T-1 is thoroughly ruggedized and will 
operate under any weather conditions of tempera- 
ture and humidity in which the batteries will 
operate. The chamber is so constructed that it 
will operate in aircraft to an elevation of at least 
36,000 feet. The meter scale changes with changes 
in the scale range, and a light is provided for 
meter illumination during night operations. 
The Victoreen Instrument Company Model 
247 (o) is an obsolete ionization 
chamber meter used extensively for 
survey work during Operation Cross- 
roads. This is a large rectangular 
box, 12 inches long, 9 inches wide, 
and 10 inches high, weighing 14 
pounds. 
B. Beta-Gamma Survey Meters 
A small light-weight, portable, gamma meas- 
uring, beta indicating survey instrument with an 
Figure 56. Victoreen model 2J+7A gamma chamber survey 
meter (/MS/PD). 
Under the handle are controls for range selection, bat- 
tery check, and zero adjustment. 
ionization chamber and a pistol grip was developed 
by the Manhattan Engineering District under the 
code name of Cutie Pie. Two such commercial 
instruments are outlined below, and it is known 
that at least one other company has produced 
models having some of these characteristics. 
Manufacturer 
Sylvania Electric 
Products Co. (i). 
Tracerlab, Inc. 
AN No 
IM-5/PD 
IM-5/PD. 
Mfg. model No.. 
RD-316 
SU-A1. 
AEC No 
SIC-7 A 
SIC-7B. 
Full scale gamma 
50 mr/hr 
25 mr/hr. 
500 mr/hr 
250 mr/hr. 
5000 mr/hr 
2500 mr/hr. 
Chamber 
3 in. diameter 
3 in. diameter. 
6 in.length 
6 in.length. 
Paper base, phe- 
B a k e 1 i t e tube 
node coated with 
coated with 
aquadag. 
aquadag. 
Beta screen 
Aluminum 0.080 in. 
Bakelite }i in. 
thick. 
thick. 
Weight 
4 pounds 
4}4 pounds. 
Dimensions of 
main body 
(length x width 
x height) in 
inches. 
6)4 x 3 x 5 
6}4 x 3 x 5. 
Figure 55. National Technical Laboratories ionization 
chamber gamma survey meter, model MX-6 (/M-40/PD). 
The range switch is at the left of the meter end of the 
handle. To the right of the meter is seen the cap over a 
recess containing sensitivity adjustment controls. A zero 
control is on the top in the foreground. RADIAC 
Figure 58. National Technical Laboratories model MX-2 
beta-gamma survey meter. 
The chamber can be seen on the left end of the case. 
The gamma shield has been removed and is showing above 
its holder at the right end of the case. 
Figure 57. Tracerlab “Cutie Pie” (IM-5/PD) . 
The chamber is the barrel to the upper right. On the 
end of the chamber is an adjustable beta window. 
The Argonne National Laboratory and its pred- 
ecessor, the Chicago Metallurgical Laboratory, 
manufactured a portable beta gamma nondiscrim- 
inating air ionization rate meter type with the de- 
tector in a probe at the end of a four-foot cable. 
This instrument, now obsolete, was called the 
Betty Snoop (o). As a matter of identification, 
this instrument was assigned the following num- 
bers: 
JAN Number AN/PDR-9 
Mfg. Model Number C2M10 
AEG Number SIC-4 A 
C. Alpha-Beta-Gamma Chamber Survey 
Meter 
A number of medium-sized instruments have 
been manufactured utilizing thin windows on one 
side of a chamber and, in some cases, discrimi- 
nating slides to give indications of alpha-beta- 
gamma radiations in terms of roentgen rates. 
These equipments will measure ionization currents 
due to soft gamma, beta, and alpha radiations. 
The National Technical Laboratories have 
manufactured a medium-sized portable survey in- 
strument utilizing an ionization chamber which 
will measure hard gamma radiation in roentgen 
rates and ionization currents due to soft gamma 
and beta radiations. This instrument is widely 
called the Beckman Meter. 
Mfg. model No MX-2. 
AEG No SIC-11A. 
Full scale gamma sen- 20, 50, 200, 500, 2000 mr/hr. 
sitivity. 
Chamber 50 in.3 bakelite coated with 
graphite. 
Window 37% in.2, 0.010 in. celluloid. 
Beta shield % in. bakelite. 
Dimensions (length x 12% x 7% x 6%. 
width x height) inch- 
es. 
Case Welded aluminum with grey 
hammertone finish. 
Weight 12% pounds. 
66 RADI AC 
Code Name 
Juno 
Pluto (o) (Sandy) 
Zeuto- _ 
Hanford Zeuto 
Zeus* (0). 
Manufacturer _ _ 
Hanford _ 
Argonne 
Victoreen 
Kelley Koett Mfg. 
Rauland. 
Co. 
Mfg. model No 
CIMI 
356 
K-340 
Z-100. 
JAN No 
IM-4/PD.. . 
AEG No 
SIC-17A 
SIC-1 A 
SIC-2 A 
SIC-2C 
Function 
Discrim i- 
Non-discriminating. 
Non-discrim- 
Non-discriminating. 
Discriminat- 
nating 
inating. 
ing. 
Full scale gamma. 
50 mr/hr 
Primarily used for 
4 mr/hr _ _ 
Sensitivity: 5,000, 
25 mr/hr. 
500 mr/hr. 
alpha with indica- 
40 mr/hr. 
50,000, and 500,- 
100 mr/hr. 
5000 mr/hr. 
tion a function of 
000 per minute. 
500 mr/hr. 
calibration. 
2500 mr/hr. 
Indication. 
Meter 
Meter 
Meter 
Meter 
Meter. 
Weight (pounds) _ 
5 
8 
6 
6 
10>i 
Dimensions (length x width 
9 x 5% x 4 
10/2 X 5/2 X 3/2 
9% x 6 x 5 
9 % x 6 x 5 
13 x 10% x 
x height) in inches. 
5%. 
*In the Model Z-100A (o), the Rauland Manufacturing Company has left off the thin window and has produced a gamma-only chamber which may, in 
some cases, be referred to as the 7eus. 
two such instruments under the trade name of 
Proteximeter which have the following character- 
istics; 
JAN No AN/PDR-2 (i)_— 
Mfg. model No 300 _ 392 (i). 
AEC No MIC-4A 
Full scale reading, 200 mr 50 r. 
Chamber in. polythylene Magenta colored. 
wall 3 in. high x 
3 in. diameter. 
Battery life 300 hr. continuous 
reading. 
Case Cast aluminum Scale colored ma- 
with grey genta. 
crackle finish. 
Dimensions Case 9 x 4 x 4}£ ex- 9 x 4 x 4}4 exclu- 
(length x width elusive of cham- sive of cham- 
x height) in ber, 7 in. over ber, 7 in. over- 
inchds. all. * all height. 
Weight 5 pounds 5}i pounds. 
A gravity switch in the top of the AN/PDR-2 
is designed to discharge the chamber when the 
instrument is inverted. A manual switch has been 
placed in the Model 392 to prevent accidental dis- 
charge as the result of inversion, vibration, or 
shock. The chamber may be detached for use 
away from the instrument base (see fig. 12). 
E. Ionization Chamber Instruments for Air- 
craft Use 
a. Gamma Intensity Meter 
Instruments which may be used to indicate 
dose rate and dosage within aircraft are now reach- 
ing the prototype evaluation stage. Such an 
instrument is the AN/ADR-1. The AN/ADR-1 
(XN-2) as it now exists consists of four units of 
approximately the following types and sizes: 
Figure 59. Rauland “Zeus”. 
The chamber occupies a space under the meter with the 
thin window on the bottom of the instrument case. 
The General Electric Company has manufac- 
tured a Zeus-type radiac set to military specifica- 
tions which is still to be fully evaluated: 
JAN No AN/PDR-20 (/). 
Full scale gamma (r/hr) 500, 2.5, .25, .025. 
Weight 10 pounds. 
Dimensions (length x width x height). 9}i x 6 x 6%. 
Beta shield }gin. bakelite. 
Alpha shield 0.003 in. aluminum. 
Window area 65% of 17 in2. 
Volume of chamber 88 in.3 
D. Ionization Chamber Group Dosimeter 
Several instruments have been devised to 
make integrated gamma dosage records. The 
Victorecn Instrument Company manufactures 
67 RADI AC 
Figure 60. The AN/PDR-20{XN-1) an experimental 
model military “Zeus”. 
Beta and gamma shields are moved by means of the con- 
trols on either side of the handle. 
(1) An indicator of the smallest standard 
size intended for panel installation, 
having the following dimensions: 2){x 
2}£x4% inches, with a 1%-inch scale. 
(2) Flight control box of dimensions 
roughly 4x6x4 inches. 
(3) Power amplifier of dimensions 10 x 
8 x 15 inches. 
(4) Receiver of dimensions roughly 10 x 
7x5 inches. 
The total weight is presently between 38 and 40 
pounds. 
The indicator includes the following char- 
acteristics: Two scales; one 0-20 mr/hr, and the 
other 0-2000 mr/hr. On one side of the scale a 
yellow light indicates dose rates of 4 mr/hr. On 
the other side of the scale a red light indicates 20 
mr/hr. At the 20 mr/hr dose rates the meter 
scale automatically changes, and other relay con- 
tacts are actuated. 
The receiver compartment contains two ion- 
ization chambers of noncoatcd stainless steel and 
filled with about 10 ml of argon gas at 50 atmos- 
pheres pressure. One chamber actuates the 0-20 
mr/hr meter scale, while the other chamber actuates 
the 0-2000 mr/hr meter scale. A radium calibra- 
tion source actuated by the flight control box checks 
instrument operation on the 0-20 mr/hr scale. 
Figure 61. Victoreen high-range “ Proteximeter”. 
The chamber is shown above the meter. A total of 50 
roentgen gamma may be recorded. 
Controls are provided to actuate external 
circuits to close ventilators, open oxygen valves, 
insert filters, etc., at predetermined levels of 
radiation intensity. 
b. Gamma Telemetering System 
Equipments capable of being dropped or 
projected into contaminated areas to relay infor- 
mation on dose rate and rate of decay are well 
advanced in development. One such unit which 
may be dropped from aircraft is the AN/USQ-1. 
F. Neutron Chamber 
In order to make a complete presentation of 
nomenclature, mention is made of the Chang and 
Eng portable survey instrument designed to 
measure fast neutrons in the presence of gamma 
radiation. The Chang and Eng consists of two 
ionization chambers, connected in parallel, with 
a quartz fibre electrometer to measure the differ- 
ence of the ionization current in the two chambers. 
One of the chambers indicates neutrons plus 
68 RADIAC 
From left to right; (a) Detector Unit, (b) Power Supply, Amplifier Unit, (c) Control Console, and (d) Panel Meter 
with automatic changeable scale and indicator lights. 
Figure 62. AN I ADR-1 (XN-2) airborne radiation detection system. 
gamma rays, the other chamber indicates only 
gamma rays. As a result the gamma ionization 
currents can be made to cancel so that the only 
indication is the ionization current indication 
of fast neutron exposure. 
15.05 Portable Alpha Proportional Counter 
The Manhattan Engineering District developed 
two portable alpha proportional counters for 
laboratory survey work. These instruments have 
virtually no usage within the military establish- 
ment and only minor commercial usage. 
Instrument 
Poppy (Walkie 
Poppy). 
Pee Wee (t). 
Design 
Argonne Na- 
Los Alamos Scien- 
tional Labora- 
tory. 
tific Laboratory. 
Manufacture 
Argonne Na- 
Nuclear Instru- 
tional Labora- 
ment and Chemi- 
tory. 
cal Co. 
AEG No 
SPC-1A 
SPC-1C. 
Mfg. No 
CLM-41 
2111. 
Case 
Grey anodized 
aluminum. 
Shape 
Rectangular. 
Dimensions 
Ill's x 5% x 8. 
Weight 
16 pounds. 
Scale readings 
0-30,000 
0-2,000, 0-20,000. 
(counts per 
minute). 
0-3,000. 
Indication 
Output meter 
Output meter 
crystal head- 
phones. 
headphones. 
Figure 63. Original “Poppy” type portable alpha propor- 
tional counter. 
A flat probe may be seen in the foreground 
Both instruments are important, since they are 
the forerunners of modern equipment being de- 
veloped by the Atomic Energy Commission and 
the Department of Defense. 
69 RADIAC 
a. Top view of the AN/PDR-10 showing meter and controls. Earphones are 
also used for indication. 
Figure 64■ Nuclear Instrument and Chemical Co. ‘‘Pee 
Wee” proportional alpha counter model 2111. 
A pencil type probe is shown to the right of the instru- 
ment case. 
An improved Poppy known as the AN/PDR-10 
(/) is in the latter stage of development. A proto- 
type form is shown in figure 65. 
Full Scale Meter Readings 
(counts per minute) 1,000, 10,000. 
Window Plyofilm window on bottom 
of case. 
Indication Meter and earphones. 
Dimensions (length x width 
x height in inches) x 4}i x 2l/i (approximate). 
Weight Approximately 5 lbs. 
b. Bottom view of the AN/PDR-10 showing holes in the bottom of the case 
covering the thin window. Several parallel wires are used for election collection. 
Figure 65. AN/PDR-10 “Poppy” type proportional alpha 
detector. 
15.06 Geigcr-Mueller Counters 
A. Commercial Portable Detectors. 
Portable Geiger-Mueller counters have reached 
the commercial market in a great number of 
different shapes and sizes. Among the better 
known survey instruments are these: 
70 RADIAC 
Manufacturer _ 
El Tronics (i) _ _ __ 
National Technical 
Nuclear Instrument 
Victoreen Instrument 
Labs. (i). 
and Chem Co. (i) (0). 
Co. (i) (0). 
JAN number 
AN/PDR-26 
IM-39/PD 
IM-8( )/PD (Set AN/ 
PDR-7). 
IM-1A/PD (Set AN/ 
PDR-5). 
Mfg. model No _ 
SMS 
MX-5 
2610 
263A. 
AEG No 
SGM-18A 
SGM-15A 
SGM-4B 
SGM-2B. 
Radiations __ _ __ 
Beta-gamma 
Beta-gamma 
Beta-gamma _ _ _ 
Beta-gamma. 
GM tube 
RCL MK-1 MDL 20. 
RCL MK-1 MDL 20, 
NICC D-12 
Victoreen VG-13. 
Wall thickness (mg/ 
Glass 30 plastic 15 
Glass 30, plastic 17_ 
Glass 35 __ 
Glass 30. 
cm2). 
Probe opening (inches) _ 
(4) ytx% (i) y4xi 
60% of 3 x circum- 
ference. 
66% of 2% x circum- 
ference. 
80% of 2 x 2y2. 
Dimensions (length x 
diameter, inches). 
7 % x 7/s 
8 x 1 
9/2 x 1 
9 x V/2. 
Probe cable length (in- 
30 
30 
36 
24. 
ches). 
Beta shield 
2mm brass _ 
Yz 2" brass 
Yz2" brass _____ 
Yz2" brass. 
Indicator _ _ _ 
Meter, earphone 
Meter, earphone 
Meter, earphone 
Meter, earphone 
(magnetic). 
(magnetic). 
(crystal). 
(crystal). 
Scale ranges (mr/hr) 
0-0.2, 0-2.0, 0-20 
0-0.2, 0-2.0, 0-20 
0-0.2, 0-2.0, 0-20 
0-0.2, 0-2.0, 0-20. 
Useful operating life 
200 
400 
200 
150. 
(hrs.). 
Weight (lbs.) 
00 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
9.6 
11.6 
13.4. 
Shape 
Rectangular 
Rectangular 
Rectangular 
Rectangular. 
Case dimensions (length 
9 z/i x 5 x 6 _ 
x 5 x 6 
11 x 6 x 4 
12% x 3/4x 8& 
x width x height in 
inches). 
Case material 
Welded aluminum 
Welded aluminum 
grey hammertone 
finish. 
Welded steel grey en- 
amel. 
Grey enamel. 
High voltage supply 
3-300 v batteries 
3-300 v batteries 
3-300 v batteries 
3-300 v batteries (one 
900 v battery in 
some). 
71 RADIAC 
Victoreen Instrument Company Model X- 
263, IM-2( )/PD (Set AN/PDR-6) 
(o). This instrument is a small light- 
weight, low voltage (300 v) Geiger- 
Muellor survey meter without a probe 
and is now obsolete because of unsatis- 
factory performance. 
The Victoreen Instrument Company Model 
263, IM-1( )/PD (Set AN/PDR-5) 
(o), the predecessor to the Model 263A 
(IM-lA/PD). This instrument has 
nearly the same physical character- 
istics but is not as fully refined as the 
263A. A Model 263B, which involves 
further improvements, has recently 
been issued. 
A great number of light-weight beta-gamma 
sensitive Geiger-Mueller counters have 
been manufactured as prospector in- 
struments. In many cases these in- 
struments do not have count rate cir- 
cuits and output meters and utilize 
earphones for their means of indication. 
Typical instruments are the Midwest 
Electronic Laboratories RD-P; Radia- 
tion Counter Laboratories Mark 11, 
Model 21, and the National Technical 
Laboratories MX-8. 
One of the original Manhattan project 
portable, beta-gamma detecting sur- 
vey instruments, utilizing a Geiger- 
Mueller tube probe supplied with high 
voltage from a vacuum tube, oscillator 
and rectifier circuit received the code 
name walkie talkie (o). The walkie 
squawkie (o) was the same type of in- 
strument. The difference being the 
talkie used headphones while the 
squawkie utilized a loud-speaker. 
Figure 66. El-Tronics model SM-3 Geiger counter 
{ANjP DR-26). 
The probe is in the well along the side of the top. 
The IM-39/PD, IM-8( )/PD, and IM-lA/ 
PD received field tests during Operation Sand- 
stone (8) which resulted in the specifications 
for the AN/PDR-T-2. This instrument will be 
described in the paragraph on military Geiger- 
Mueller counters. Other commercial instruments 
which have had some military use and which 
should be noted are: 
72 RADI AC 
The probe is mounted horizontally in the well along the top of the case. The range is to the left of the handle. 
The phone jack and zero adjustment are out of sight at mid-case. 
Figure 67. National Technical Laboratories model MX-5 Geiger Counter (/M-391 PD). 
Figure 68. Nuclear Instrument and Chemical Company model 2610 Geiger counter (AN/PDR—7). 
The probe is shown mounted in clips on the end of the instrument. The probe beta shield is open. 
73 RADIAC 
Figure 69. Victoreen Instrument Company model 263A 
Geiger counter (AN/PDR-5). 
The probe (foreground) is carried in the brackets at one. 
end of the instrument case. The switch and phone jack 
are located mid-case under the handle. 
Figure 70. Recent commercial improvements in portable Geiger-Mueller survey meters. 
Left; the Nuclear Instrument and Chemical Company Model 2610A with the probe held in a recess in the handle, 
Right; the Victoreen Instrument Company Model 263B which involves some improvements over Models 263 and 263A, 
74 RADIAC 
B. Military Portable Geiger-Mueller Detectors 
JAN number 
a. AN/PDR-8 (/) 
b. AN/PDR-8A (/) 
c. AN/PDR-8B (/) 
d. AN/PDR-8C (/) 
AN/PDR-15 (/) 
AN/PDR-27 it) 
AN/PDR-T-2 (i). 
Manufacturer 
a. Hoffman 
b. R. C. A. 
c. Hoffman 
d. Admiral 
General Electric _ 
El-Tronics (model 
PR-2). 
Radiation 
Beta-gamma 
Beta-gamma 
Beta-gamma 
Beta-gamma. 
Scale ranges (mr/hr) _ 
a. Calibrated in r/24 hr. b, 
0-0.5, 0-5.0, 0-50, 0- 
0-0.5, 0-5.0, 0-50, 0- 
0-0.5, 0-5.0, 
c, d. 0-0.5, 0-5.0, 0-50, 
0-500 (beta indication 
on first two scales). 
500 (beta indication 
on first two scales). 
500 (beta indication 
on first two scales). 
0-50. 
Detector 
BS-1; halogen-filled mica 
BS-1; halogen-filled mica 
BS-1; halogen-filled mica 
RCL MK-1 Mdl 
end window (first two 
scales). BS-2, low sensi- 
tivity halogen tube (3rd 
and 4th scale). 
end window (first two 
scales). BS-2, low sen- 
sitivity halogen tube 
(3rd and 4th scale). 
end window (first two 
scales). BS-2, low sen- 
sitivity halogen tube 
(3rd and 4th scale). 
21. 
Beta window (mg/ ’ 
3-4 
3-4 
3-4 
30. 
cm2). 
Window area (in.2).. 
0.44 
0.44 
0.44 
8 openings }'■2 in. x 
l/e in. 
Indicator.. 
Meter plus headphones 
Meter plus head- 
phones. 
Meter plus head- 
phones. 
Meter plus head- 
phones. 
Probe dimensions 
8 X lf8 X 1 Y% in _ 
73/i x 1% x in. dia 
8 x 1% x l3/s in 
8% x % in. dia. 
Length of probe 
60 in 
60 in . __ 
60 in 
36 in. 
cable. 
Form factor 
Kidney-shape 
Rectangular “flat iron”. 
Rectangular 
Rectangular. 
Dimensions (length x 
io x ey2 x 7 
ll/4 x 4% x 3% 
9}i x 53/i6 x 4y2 
10 x 6 x 7. 
width x height in 
inches). 
Weight (pounds) 
a. 14.1 
b. 11.5 
c. 12.8 
d. 11.5 
11 
10.2 
9.5. 
Power supply 
a. Electronic vibrator 
b. Vibrator(sub-miniature 
tubes). 
c. Neon oscillator 
d. Vibrator (sub-miniature 
tubes). 
Electronic vibrator 
Neon oscillator (plug 
in electronic unit). 
3-300 v batteries. 
75 
871748°—50——7 RADIAC 
a. Kidney-shaped radiac set AN/PDR-8. 
b. AN/PDR-8 with probe. 
The tube is vertically held in a box on the right of the 
instrument. The extension pole is collapsed in a box on 
the left. Carrying straps are shown. 
The extension pole with the end window tube probe is 
shown. 
Figure 71. Geiger counters AN/PDR-8 (series) 
Figure 72. Geiger counter AN/PDR-15. 
The end window tube holder is placed in the hole between the two control knobs when not used at a distance 
from the body of the instrument. 
76 RADI AC 
a. The probe case with thin end window Geiger tube is shown in foreground 
Figure 73. Radiac set AN/PDR-27. 
b. Side view of case with probe vertical in holder at the right end of instrument. 
This instrument was originally known as the AN/PDR-8E. 
These radiac equipments have automatic scale 
number-changing devices with changes in scale 
ranges. The AN/PDR-T-2 has an illuminated 
dial for night operation. The AN/PDR-8 series 
is supplied with a fish-pole type of extension (36 
inches) for probe examinations at a distance from 
the instrument (see fig. 29). The probe of the 
AN/PDR-15, and also of the AN/PDR-27, is 
carried in a vertical hole through the instrument 
case, so that when the instrument is being held 
by the handle, the beta window is exposed to the 
ground to facilitate ground beta survey work. 
The AN/PDR-T-2 is intended as an interim 
training instrument and is the combined result 
of the Sandstone evaluations (8). 
C. Monitors Utilizing Geiger Detection 
a. A number of instruments are manufactured 
commercially as monitors for detecting gamma 
radiation. The majority give an audible signal, 
either as amplified Geiger clicks or as a buzz, 
when a predetermined level of radiation is reached, 
and as a result some have been called squawkers, 
etc. The Geophysical Instrument Company 
Model 600 is a good example. This instrument 
causes an alarm to sound intermittently at gamma 
intensities of about 0.1 r with the frequency in- 
creasing to continuous alarm at 0.14 r. 
b. Probably the most important of the 
presently available monitoring instruments are 
the hand and foot monitors (i) such as the com- 
mercial equipment manufactured by the Kelley- 
Koett Manufacturing Company: 
JAN number, AN/UDR-3. 
Mfg. model number. _K-240. 
AEG number CGM-17B. 
Dimensions 67 in. high, 36% in. wide, 22 in. deep. 
Weight 600 pounds. 
Power 115 v 60 cycle A. C. 
There are five scaling systems with registers as 
follows: 2 GM tubes for palm and back of each 
hand (4 systems with a total of 8 tubes) and 4 GM 
tubes for the feet. An over-all total of 12 GM 
tubes. The tubes are sensitive to beta particles 
having energies greater than 160 Kev. The 
approximate warning level is 15 counts (including 
background) in 24 seconds for the feet. 
77 RADI AC 
Figure 74. The AN/PDR-T-2 Geiger-Mueller survey meter. 
A push-button for scale illumination is on the meter end of the handle. The shield on the tube probe is open, and the 
Geiger tube may be seen. Scale range—battery check switch and zero adjustment are partially obscured by the handle. 
A hand and foot monitor, manufactured to 
military specifications, has reached an advanced 
state of development: 
Manufacturer Radio Corporation of America. 
JAN number AN/UDR-10 (/). 
Mfg. model number. _ EMA-2B. 
AEG number CGM-T4A. 
Dimensions (inches) 
(approximate): 
Pedestal 60 high, 48 wide, 30 deep (at base). 
Control Unit 42 high, 30 wide, 18 deep. 
Weight (pounds) 
(approximate): 
Pedestal 750. 
Control cabinet. 250. 
Power 95-135 v, 60 cycle A. C. 
Figure 75. Geophysical Instrument Company model 600 
monitor. 
The Geiger tube case is shown at the lower right. 
78 RADI AC 
The AN/UDR-10 is designed to operate 
automatically and indicate the degree of con- 
tamination of five selected areas as follows: 
right hand—back 
right hand—palm 
left hand—back 
left hand—palm 
soles of both right and left shoes 
Counts for each of the selected areas are separately 
channeled into five counting and recording 
systems. This unit has been designed for the 
convenience of both organization and personnel. 
Several pedestals may be placed in exit gates, etc., 
at any distance from the control cabinet which 
can be located; for example, in a guard house. 
Indication is by means of signal lights on both 
the pedestal and control cabinet. 
15.07 Photomultiplier Survey Meters 
JAN number 
AN/PDR-11 (/)__. 
AN/PDR-18 (/). 
Radiation detect- 
ed. 
Alpha 
Gamma. 
Scale range- 
Up to 10,000 d/ 
min. 
0.5, 5, 50, 500 r/hr. 
Detector 
Phosphor and 
Phosphor and 
photomultipli- 
ers in probe. 
photomultiplier. 
Indication 
Output meter or 
headphone. 
Output meter. 
Weight (pounds) _ 
12 
8y% (maximum). 
Case dimensions 
6 x 3 x 12 
6 x 4 x 10 (ap- 
(length x width 
x height in 
inches). 
prox.). 
Both instruments are involved with later stage 
development and production engineering under 
direction of Bureau of Ships and should be ready 
for field test in 1950. 
Figure 76. Kelley-Koett model K-2J+0 hand and foot counter 
{AN/ U DR-3). 
79 RADIAC 
Figure 77. AN/UDR-10 five-channel counter for detecting heta-gamma contamination of the hands and feet. 
Plastic envelopes in the hand holes may be changed after contamination. At the lower left is a box containing a 
roll of paper which replaces the paper covering the area used to monitor the soles of shoes. 
80 RADI AC 
1 5.08 Film Badge 
Dental film size packets, l}i x 1% inches not 
including waterproof coverings. 
Useful sensitivity range- 
-Roentgens* 
Emulsion 
Maximum 
Maximum 
density of S 
density of 6 
Ansco non-screen 
__ 0.03-2.0 
7. 5 
DuPont 502 
0.03-3.0 
Eastman Type K 
0.05-1.0 
10 
Ansco Super Ray 
0.2-3.0 
20 
DuPont 552b _ _ 
0.5-10 
DuPont 552a 
__ 4-20 
60 
Eastman type A 
1.0-10 
15 
Eastman Cine Pos. 5301 
0.5-80 
250 
DuPont 605 
10-250 
2, 600 
Eastman Cine Pos. fine grain 40-400 
1, 000 
5302. 
Eastman Kodalith 6567 
70-700 
Eastman Kodabromide G-3. 
470-8,000 
Eastman 548-0 double coat_ 
__ 2,000-10,000__ 
Eastman 548-0 single coat__ 
5,000-20,000__ 
50, 000 
*The sensitivity range of these film emulsions depends upon the choice of 
developer. Some nominal values are given which may be altered by as much 
as a factor of 100 through the use of different developing solutions. Densi- 
tometers (see page 35) having a top density reading of 3 have been in general 
photographic use for a number of years. The Weston Electrical Instrument 
Corporation manufactures such an 
instrument having a model number 6. 
The Ansco Division of the General Aniline and Film Oorp. have recently 
marketed a Model 12 color densitometer which can measure a density of 6. 
Figure 78. AN/PDR-11 (XN- ) alpha survey meter. 
The sensitive window is to the rear left of the probe in 
the picture foreground. 
81 RADIAC 
Figure 79. AN/PDR-18 gamma 'photomultiplier survey meters. 
Two models are shown with experimental form factors. The final instruments may have no resemblance to those shown 
82 REFERENCES* 
(1) Radiological Defense, Volume I. Joint Cross- 
roads Committee, 1948. 
(2) Lapp, R. f. and Andrews, H. L. Nuclear Radiation 
Physics. Prentice-Hall, 1948. 
(3) Strong, John. Procedures in Experimental Physics. 
Prentice-Hall, 1941. 
(4) Rossi, B. and Staub, H. H. Ionization Chambers 
and Counters: Experimental Techniques. Mc- 
Graw-Hill, 1949. 
(5) Korff, S. A. Electron and Nuclear Counters: 
Theory and Use. D. Van Nostrand, 1946. 
(6) Yagoda, H. Radiation Measurements with 
Nuclear Emulsions. Wiley, 1949. 
(7) Pollard, Ernest and Davidson, W. L. Applied 
Nuclear Physics. Wiley, 1942. 
(8) Andrews, H. L. and Campbell, D. C. Evaluation 
of Radiological Survey Instruments used for 
Health Protection during Operation Sandstone. 
Restricted. Sandstone Scientific Director’s 
Report 31, Annex 10, 1 April 1949. 
(9) Radiological Defense, Volume III. Armed 
Forces Special Weapons Project, 1949. 
(10) Radiation Instrument Catalog. U. S. Atomic 
Energy Commission, Technical Infor- 
mation Branch, 1949. 
•A more complete bibliography will be found in Nucleonics 1,68 (December 1947). Other bibliography and references which may be of interest to the reader 
can be found appended to Reference (9). 
83 Appendix I 
A-N NOMENCLATURE LIST 
The following table lists A-N numbers for equipments now in field use or anticipated for use in the 
near future. It should be noted that this is far from a complete listing. 
Nomenclature 
Instrument 
AEG No. 
Manufacturer 
Model 
Trade or code name 
AN/ADR-T 
Airborne gamma dose 
rate. 
Airborne dosimeter. 
AN/ADR-2 
AN/PDR-2 
Ion chamber group dosi- 
meter. 
Pocket dosimeter 
MIC-4A. _ 
Victoreen 
300. 
Proteximeter 
AN/PDR-3: 
IM-9/PD 
PIC-7A. 
Kelley Koett 
K-100 
IM-9A/PD 
Pocket dosimeter 
Kelley Koett. 
K-110 
PP-311A/PD 
PP-354B/PD 
AN/PDR-4: 
DT-16/PD 
Charger 
AV-2D 
Kelley Koett 
K-135 
Charger. _ 
Kelley Koett 
Pocket chamber 
PIC-2C 
Victoreen _ _ 
352. 
DT-16A/PD 
PP-316/PD 
AN/PDR-5: 
(IM-1A/PD) 
AN/PDR-7: 
(IM-8( )/PD)_ 
AN/PDR-8 
Pocket chamber 
PIC-1B 
Nuclear Instrument and 
3340 
Charger-reader 
AE-2A 
Chemical Co. 
Victoreen 
287 
Minometer. 
Portable G-M detector 
SGM-2B _ 
Victoreen 
263A 
Portable G-M detector 
Portable G-M detector 
SGM-4B 
Nuclear Instrument and 
Chemical Co. 
Hoffman 
2610 
AN/PDR-8A 
Kidney shaped G-M 
Radio Corporation of 
America. 
Hoffman 
AN/PDR-8B 
Portable G-M detector 
AN/PDR-8C 
Portable G-M detector 
Admiral 
AN/PDR-9 
Beta-gamma ion cham- 
ber. 
Portable alpha propor- 
tional counter. 
Alpha scintillation 
counter. 
Portable G-M detector 
SIC-4A 
Argonne National 
Laboratory. 
General Electric 
C2M10 
Betty Snoop. 
Poppy. 
AN/PDR-10 
AN/PDR-11 
Radio Corp. of America. 
AN/PDR-15 
AN/PDR-18 
Gamma scintillation 
AN/PDR-20 
counter. 
Beta-gamma descrimi- 
nating chamber. 
Pocket chamber 
General Electric _ 
Zeus. 
AN/PDR-21; 
DT-35( )/PD_ 
PP-43( )/PD__ 
AN/PDR-26 
PIC-2E. 
Kelley Koett 
K-700 
Ch ar ger-reader 
AE-1B 
Kelley Koett 
K-425 
SGM-18A 
El-Tronics 
SM3 
AN/PDR-27* 
Portable G-M detector 
General Electric 
AN/PDR-T-1 
SIC-18A 
Kelley Koett 
K-350 
AN/PDR-T-2 
Portable G-M detector 
El-Tronics 
PR-2. __ 
AN/UDR-3 
Hand and foot monitor 
CGM-17B 
Kelley Koett _ 
K-240 
AN/TTDR-10 
Hand and foot monitor 
CGM-T4A.. 
Radio Corp. of America.. 
EMA-2B__ 
*The AN/PDR-27 was once known as the AN/PPR-8E. 
85 RADIAC 
Nomenclature 
Instrument 
AEC No. 
Manufacturer 
Model, name 
Trade or code name 
AN/USQ-1 
Gamma telemetering 
IM-3/PD 
Ion chamber survey 
SIC-9B 
Victoreen . 
247A 
IM-4/PD__ 
Alpha-beta-gamma ion 
SIC-2 A 
Victoreen 
356. 
Zeuto. 
chamber. 
IM-5/PD 
Beta-gamma ion chamber. 
SIC-7 A 
Sylvania 
RD-316 
Cutie pie. 
SIC-7B 
Tracer Lab 
SU-1A 
Cutie pie. 
IM-7A/PD 
Drift meter 
SIC-5 A. . 
Kelley Koett 
K-320 
IM-39/PD 
Portable G-M detector 
SGM-15A 
National Technical Lab- 
MX-5 
oratories. 
IM-40/PD. 
Ion chamber survey. 
SIC-15A. _ 
National Technical Lab- 
MX-6 
oratories. 
IM-50/PD 
Pocket dosimeter. 
PIC-10A 
A. 0. Beckman Co 
IM-51/PD. 
Pocket dosimeter 
PIC-9A.. 
Cambridge Instrument 
BM 17400 
Co. 
PP-354A/PD 
Dosimeter charger 
Chatham Electronics 
PP-527/PD 
Dosimeter charger 
AY-7 A 
Cambridge Instrument 
Co. 
86 APPENDIX II 
GLOSSARY OF TERMS CONCERNED WITH RADIAC INSTRUMENTS 
Avalanche The action within proportional and 
Geiger counters in which one ion 
(electron) produces another ion 
by collision, these two ions (elec- 
trons) producing still further 
ionization. 
Background The background count is that 
which is caused by any agency 
whatever other than the radia- 
tion which it is desired to detect. 
For health protection, it usually 
includes the radiations produced 
by naturally occurring radio- 
activity and cosmic rays. 
Calibration The process of checking and ad- 
justing instrument operation 
against known sources of radio- 
activity. 
Chamber A container in which ionization is 
allowed to take place and in 
which all the original ions are 
collected—otherwise known as 
an ion chamber. 
Count A terminated discharge produced 
by an ionizing event in a counter 
tube. 
Counter A device, such as a proportional 
counter or a Geiger-Mueller 
counter, which responds to or 
counts individual ionizing 
events. 
Count rate The instrument used to indicate 
meter. the rate of counts indicated by a 
counting chamber or a propor- 
tional or Geiger counter. It 
may be used with both portable 
and laboratory equipment. 
Curie.. The curie is a standard measure of 
the rate of radioactive decay 
equal to 3.7 x 1010 disintegra- 
tions per second. 
Dead time The time interval between individ- 
ual counts in which a counter is 
insensitive. 
Densitometer__ Electronic-Optical device used to 
determine the density (blacken- 
ing) of film badges. 
Dosimeter An individual dosage indicating 
device—more specifically, a 
direct reading quartz fibre elec- 
troscope sensitive to gamma 
radiation and about the size of a 
fountain pen. Otherwise known 
as a pocket dosimeter, a pocket 
electroscope, or a quartz fibre 
dosimeter. 
Electrometer A specially constructed vacuum 
tube. tube used for the amplification 
of minute currents such as those 
obtained from ionization 
chambers. 
Film badge A small packet containing photo- 
graphic film which is used to 
obtain individual radiation dos- 
age readings. Readings are 
primarily of gamma radiation. 
Geiger counter_ A low dose rate, high sensitivity 
detector of beta and gamma 
radiations. It may be either a 
light-weight portable detector or 
a laboratory instrument. Also 
known as a Geiger-Mueller 
counter. 
Geiger region _ _ The part of the characteristic 
curve of pulse size as a function 
of voltage in which the size of 
the pulse is independent of the 
magnitude and type of radiation 
producing the initial ionizing 
event. 
Half life The time required for the disinte- 
gration of a radio-isotope to 
one-half of its initial rate of 
activity. 
87 RADIAC 
Ionization The process by which a neutral 
atom or molecule loses an elec- 
tron with the remaining ion 
becoming positively charged and 
the electron and positive ion 
forming an ion pair. 
Ionization A high dose rate, low sensitivity 
chamber instrument for the measure- 
survey ment of gamma radiation— 
meter. also known as a gamma survey 
meter or an ion chamber. 
Photographic The entire operation required to 
dosimetry. obtain individual dosage records 
by the use of film badges. This 
includes calibration, film devel- 
opment, densitometry, etc. 
Plateau The roughly horizontal part of the 
counting rate as a function of 
voltage curve in which there is 
very little change in count rate 
with change in voltage. 
Pocket cham- A non-self-reading individual gam- 
ber. ma dosage indicating device 
about the size of a fountain pen. 
Proportional An instrument which counts alpha 
counter. particles and descriminates 
against counts produced by beta 
and gamma radiations. It may 
be either a portable or a labora- 
tory instrument. 
Proportional The portion of the characteristic 
region. curve of pulse size as a function 
of voltage in which the size of 
the pulse is proportional to the 
number of ions formed by the 
initial ionizing event. 
Quenching The process of extinguishing the 
action within a Geiger counter 
tube. External quenching uti- 
lizes an electronic circuit. A 
self-quench is produced by ac- 
tion within the counter tube. 
Recombina- The process of union between 
tion. electrons and positive ions to 
form neutral atoms or mole- 
cules—the opposite of ioniza- 
tion. 
Recovery time_ The time interval after recording 
a count before the pulses pro- 
duced by the next ionizing event 
in the counter are of substan- 
tially full size. 
Region oj con- The part of the characteristic 
tinous dis- curve of pulse size as a function 
charge. of voltage in voltages higher 
than those of the Geiger region. 
In this region the tube goes into 
a state of continuous discharge. 
Region 0/ Urn- The part of the characteristic 
ited propor- curve of pulse size as a function 
tionability. of voltage in which the gas 
amplification depends both up- 
on the numbers of ions produced 
in the initial event and upon the 
voltage (very little use). 
Roentgen For military purposes, this is a 
unit of dosage for the measure- 
ment of gamma radiation. This 
is the quantity of radiation 
which, under standard condi- 
tions, produces 2.08 x 109 ion 
pairs per cc of air. 
Scaler A laboratory electronic device 
used to record the number of 
pulses from a counter. An elec- 
tronic circuit capable of divid- 
ing the incoming pulse rate by a 
constant factor so that mechani- 
cal methods of recording the 
pulse may be used. 
Threshold In the Geiger counter character- 
istic curve there are two thresh- 
olds: (a) The voltage below 
which no pulses are recorded is 
the characteristic curve thresh- 
old, and (b) the voltage at 
which the plateau starts is 
known as the threshold of the 
Geiger region. 
Scaler__ 
88 SUBJECT INDEX 
Page 
Accelerators 39 
Air-borne gamma intensity meter 67 
Air contamination 49 
Aircraft instruments 67 
Air explosion 47 
Air survey 47 
Alpha calibration 45 
Alpha particles 3, 11 
Alpha particles, detection 48 
Alpha track measurement 47 
Anticoincidence circuit 28 
Atomic bomb explosion 47 
Avalanche ionization 21, 87 
Background 26, 87 
Batteries 22 
Beckman meter 66 
Beta calibration 45 
Beta particles 3, 11, 50 
Betatron 39 
Betty Snoop 66 
Bevatron 39 
Calibration 45,87 
Calibration, alpha 45 
Calibration, beta 45 
Calibration, gamma 45 
Calibration, sources 45, 56 
Chamber, cloud 39 
Chamber, pocket 9, 59, 88 
Chang and Eng 68 
Chemical dosimeters 31 
Cloud chamber 39 
Cobalt 60 calibration source 45 
Coincidence circuit 28 
Color code 42 
Color crystals 31 
Color liquids 31 
Compton effect 4 
Continuous discharge region 21, 88 
Copper salts 32 
Count rate meter 29, 56, 87 
Crystals 31 
Curie 45, 87 
Cutie Pie 66 
Cyclotron 39 
Decontamination 47 
Densitometer 35, 87 
Disposable covers 41 
Dose, permissible 51 
Dosimeter charger 7, 59 
Dosimeter, group 47, 67 
Dosimeter, pocket 7, 59, 87 
Drift meter 8, 63 
Dust collector 56 
Dyes 81 
Page 
Electret 33 
Electrical characteristics 43 
Electrical characteristics (pressure effects) 43 
Electrical characteristics (saturation effects) 43 
Electrical characteristics (temperature effects) 43 
Electrical characteristics (time constant 43 
Electrical characteristics (zero) 43 
Electrometer 7, 9 
Electrometer circuit 10 
Electrometer tube 13, 87 
Electron 3 
Electroscope 7 
Fall-out 47 
Field laboratory 55 
Field survey 14,25,55 
Film badge 35,47,81,87 
Film badge, characteristic curve 36 
Film badge densitometry 35 
Film badge marking 35 
Film badge processing 36 
Food contamination 49 
Gamma calibration 45 
Gamma rays 3, 51 
Gas amplification 15, 19 
Geiger-Mueller counter 21, 47, 70, 87 
Geiger-Mueller counter, characteristic curve 22 
Geiger-Mueller counter, plateau 22, 88 
Geiger-Mueller counter probe 26 
Geiger-Mueller counter, pulse 21 
Geiger-Mueller counter, quenching 22, 88 
Geiger-Mueller tube 24 
Geiger-Mueller tube, dead time 22 
Geiger-Mueller tube fillings 24 
Geiger-Mueller tube life 24 
Geiger-Mueller tube, low voltage 22 
Geiger-Mueller tube window 24 
Geiger region 22, 88 
Ground explosion 47 
Group dosimeter 47, 67 
Half-life 45,88 
Hand and foot counter 57, 77 
Health records 38 
Helium nuclei 3 
High resistance 13 
Hydrogen nuclei 3 
Instrument characteristics 41 
Instrument characteristics, case 41 
Instrument characteristics, center of gravity 41 
Instrument characteristics, handle 41 
Instrument characteristics, illuminating light 42 
Instrument characteristics, meter marking 42 
Instrument characteristics, meter time constant 43 
89 RADIAC 
Page 
Instrument characteristics, pressure and temper- 
ature effects 43 
Instrument characteristics, saturation effects 43 
Instrument characteristics, strap 41 
Instrument characteristics, switch knobs 42 
Instrument characteristics, weight 41 
Instrument use 47 
Insulation 13, 49 
Ion pair 4 
Ionization 4, 87 
Ionization of air 4 
Ionization chamber _ 5, 7, 87 
Ionization chamber characteristics 10 
Ionization chamber characteristics, circuit 13 
Ionization chamber characteristics, gas 12 
Ionization chamber characteristics, pressure 12 
Ionization chamber characteristics, volume 13 
Ionization chamber characteristics, wall 12 
Ionization chamber characteristics, window- 11 
Ionization chamber survey meter 14, 47, 64, 87 
Ionization chamber survey meter, thin windows 11, 66 
Ionization current 10 
Juno 67 
Laboratory 55 
Landsverk electroscope 8 
Lauritsen electroscope 7 
Limited proportional region 19, 21, 88 
Lindemann electrometer 10 
Linear accelerators 39 
Mercury salts 32 
Meter, illumination 42 
Meter, marking 42 
Meter, time constant 43 
Minometer 62 
Monitors 77 
Neher-Harper circuit 23 
Neutron 3, 68 
Nuclear track plates 50, 56 
Pair production 4 
Pee Wee 69 
Personnel monitor 55 
Phosphors 31 
Photo conduction 31 
Photoelectric cell 13 
Photoelectric effect 4 
Photographic Dosimetry 35, 88 
Photomultiplier survey meter 79 
Photomultiplier tube 32 
Physical characteristics 41 
Physical characteristics, center of gravity 41 
Physical characteristics, dimensions 41 
Physical characteristics, handle 41 
Physical characteristics, scale illuminating 42 
Physical characteristics, scale marking 42 
Physical characteristics, shoulder strap 41 
Physical characteristics, volume 41 
Physical characteristics, weight 41 
Pluto 67 
Page 
Plutonium calibration source 45 
Pocket chamber 9, 59, 88 
Pocket chamber charger-reader 9, 62 
Pocket dosimeter 7, 59 
Pocket dosimeter charger 7, 59 
Poppy 69 
Positron 3 
Pressure effects 43 
Proportional counter 19, 47, 69, 88 
Proportional counter gas 19 
Proportional counter, gas flow 56 
Proportional counter probes 19 
Proportional region 19, 88 
Proteximeter 67 
Proton 3 
Quartz fiber dosimeter 7, 59 
Quartz fibre drift meter 8, 63 
Quench circuits 23 
RADI AC, definition 1 
Radiation 3 
Radio waves 3 
Radium calibration source 45 
Remote reading equipment 68 
Resistors 13 
Roentgen 51, 88 
Sandy 67 
Scaler 27, 56, 88 
Scaling circuits 27 
Scintillation counter 32 
Scintillation crystals 32 
Solid excitation 31 
Spectral response 12, 43 
Squawker 77 
Strontium 90 calibration source 45 
Synchrocyclotron 39 
Synchrotron 39 
Telemetering equipment 68 
Temperature effects 43 
Thimble chambers 9 
Thin window chamber 11, 66 
Townsend avalanche 21 
Under-ground explosion 47 
Under-water explosion 47 
Uranium calibration source 45 
Vacuum tube electrometer 10 
Vacuum tubes, electrometer 13 
Vacuum tubes, electron multiplier 32 
Van de Graaf generator 39 
Walkie poppy 69 
Walkie squawkie 72 
Walkie talkie 72 
Water contamination 49, 56 
Windows 11 
Wulf electrometer 10 
X-rays 3 
Zero set 43 
Zeus 67 
Zeuto 67 
90